Broccoli and potato soup is a classic, and deservedly so. Utilizing fantastic ingredients at their winter's best, this soup manages to be hearty and warming without ending up heavy. When eaten on a cold, rainy day, it's comforting but doesn't put you right to sleep, and thus serves as a refreshing respite from rich, mid-winter braises, especially when spring produce is still a month or so out.
Much like you, I imagine, before I made this soup I did a quick internet search to see how other folks went about it. Most recipes looked like they would yield a tasty enough soup, but they also all seemed to go about doing so in the same manner, adding what I saw as superfluous ingredients while neglecting others.
The top three offenders were:
1: Chicken stock. Nearly every recipe defaulted to using it as the liquid. Now don't get me wrong, I love chicken stock, I think it's essential that you know how to make it, and you should use it often, but I don't think it has a place in every single meal. This is a vegetable soup, and it shines as a vegetable soup. Adding chicken stock here is kinda like adding a guitar solo to an acoustic folk song. It doesn't fit the aesthetic. Will chicken flavored broccoli soup taste bad? Of course not. But it will taste like chicken flavored broccoli soup. And that's not what I set out to make.
2: Cream and cheese. A great many recipes call for adding cream or milk at the end of the cooking process and garnishing with cheese. Again, this is the same sort of unnecessary augmentation as adding chicken. Are creamy, cheesy soups delicious? Of course they are. But are cream and cheese necessary? Not at all. In fact, in a soup like this where the flavors are delicate, adding dominate, palate coating ingredients like cream and cheese can quickly turn your broccoli soup into a creamy cheese soup with a green tint. It would taste great, but not in a way that highlights what's great about the vegetables.
3: Throwing out leek greens and broccoli stems.
Leeks aren't actually a common addition to this soup, but I like them and because they play a starring role in leek and potato soup, I figured it was time for all three to get together in what Kanye likes to call a ménage. Leeks and broccoli both though suffer from the problem of severe neglect. Their whites and florets respectively are their rhino's horn, cooks cut off the most desirable part and just throw the rest away. Which is a shame because rhinos are delic...I mean, leek greens and broccoli stems are not only food, they're quite tasty food at that. They just need a little more attention to get there.
Broccoli stems have woody exteriors that need to be trimmed off, but once you do that, their cores are crisp and taste exactly like, get this, broccoli. So if you are making a dish that highlights the florets alone—like I don't know, maybe this grilled cheese sandwich—then save the stems for later and purée them into soup. That's exactly what I did. You're welcome to follow suite.
Leek greens are much more fibrous than their paler counterparts to the south, so they work well in similar preparations as tough cuts of meat, i.e. long braises and cut across the grain. Left whole and braised out for a couple hours in veg stock and white wine, they are all sorts of amazing. I've been thinking a lot recently about how to combine leek greens, sausage, and mashed potatoes. Like maybe a braised out shepard's pie? Not sure yet, but I'll let you know when I get there.
Aside from braises, leek greens are fantastic additions to...
...stock. Like this vegetable one here. Remember how I said in the first complaint (oh, and this ends the numbered complaint part of this post, the rest will be the recipe and scattered, unorganized whining) that adding chicken stock was a bad idea because it overwhelmed the vegetables? Well, then why not add vegetable stock instead? Especially one made with the exact same vegetables as the soup itself? That's what I did here. If you notice, the stock pot (or pressure cooker in this case) contains leek greens, broccoli stem trimmings, and potato skins. Instead of throwing all that stuff out, making a stock out of those scraps extracts their flavors and adds it back to the soup. So rather than competing for the spotlight, the stock here is backing up the stars of the show. I also added some onion scraps, a carrot, a piece of konbu, and some thyme. All great but not necessary.
Fifteen minutes in the pressure cooker was enough to make this stock that is perfectly tailored for the soup. No pressure cooker? No problem. Just simmer everything a bit longer. 45 minutes should do the trick.
With the vegetable stock simmering, now's a great time to focus on the potatoes. I like fluffy Russets here. One regular sized, meaning kinda large, Russet should be sufficient. A couple Yukon Golds would work too. If you didn't already skin them for the stock, do that, go back in time, and add the skins to the stock. If reserving the peeled potatoes for a while, remember to keep them submerged in water, as they discolor quickly. Cut the potatoes up into big chunks, cover with water in a pot, and then heat that to about 140-155F. Hold the potatoes in that mildly hot, but pre-simmering water for a half hour, then strain them out and submerge them in cold tap water.
Why go through this step? Well, potatoes contain a lot of starch, and if you cook them at very high, boiling temperatures, then that starch runs the risk of absorbing too much water and rupturing. In and of themselves, ruptured starches aren't too terrible as long as you don't agitate them, but this soup is destined for the blender, which I would say is quite agitating. A few spins in said blender and all those ruptured starches could very well turn the whole soup gluey and gummy. A lot of recipes combat this by telling you not to over-blend the soup, but that's not guaranteed effective and leaves you with a still slightly lumpy result. Instead, adding this step where you hold the potatoes around 150F for a half hour and then cool them back down under 100F essentially traps those starches and prevents them from later ruining the party, allowing you to confidently blend to a pleasantly smooth consistency.
Now's as good a places as any to make a standard sort of list of ingredients:
- Head of broccoli, stem peeled and chopped. Exterior thrown in the stockpot, cores reserved.
- 1 good sized leek (consult the picture toward the top of the post), whites and pale green parts sliced and cleaned. Dark green parts cleaned and thrown in the stockpot.
- 1 Russet potato. Not small. Skin throw in the stockpot, non-skin parts chopped up and pre-cooked in the manner described above.
- Half an onion. If you want. Chop it up too.
- 1tsp mustard seeds. Ground.
- Salt and black pepper to taste.
- White wine or champagne vinegar to taste. Probably a tablespoon or so.
- Chili flakes and cayenne pepper, also, get this, to taste.
- Garlic? Sure. Cut up a clove.
- MSG. Seriously. A half teaspoon should do the trick.
- That vegetable stock you made. Or just some water.
- Fancy assed olive oil, because you deserve it.
The soup itself is easy to make. Sauté the onions and leeks in a generous amount of cheap olive oil until soft. Add the garlic, chile flakes, and ground mustard seeds. Then stir a for thirty seconds or until the garlic becomes fragrant.
Mustard works quite well here brightening up the dish, but it's easy to go too far. I prefer the seed to actually adding prepared mustard.
Once the garlic is fragrant feel free to add a half cup of white wine and reduce that until almost gone. I keep a box of decent but by not means good white wine on hand for occasions such as this. No white wine, skip it. Add the potatoes, peeled broccoli stems, and about half the florets. Pour in the strained vegetable stock until everything is covered.
Bring to a simmer, then cover with a lid and drop the heat to low. Cook until the potatoes are tender, about 15 minutes.
Add a half teaspoon of MSG. Granted, I used konbu in the veg stock, so the soup already had a decent amount of glutamates floating around, buy why not add a little more right? Right! It's easy to overdo it with MSG, and too much is gross. So be gentle. A half teaspoon should be sufficient.
And don't even be a hippie about this. Science says it's fine.
Blend until smooth with a stick blender or a regular old blender. A food processor won't do the greatest of jobs here, but you know, work with what you've got. Taste your soup. It's probably pretty good, but I bet it could use something to brighten it up just a tad. Splash a dash some white wine vinegar in there and taste it again. See what I mean? Go to town adjusting the salt, chile flakes, and black pepper until you think it tastes good. Helpful hint, add more salt than you think.
Grill up some crusty bread and then rub a clove of garlic all over it.
Remember those florets of broccoli I told you to reserve. Now's a great time to charr them, a la the technique in this post.
Once the soup is securely in a bowl, top it with the charred broccoli, a dash of cayenne, some more black pepper, a grating of lemon zest, and some fancy olive oil.
Eat quickly while watching not-so legal streams of the new Top Gear Episodes.
Oh, and yes, the elephant in the room: Is this soup vegan? No. Well, I mean, yes, vegans can eat it and in no way violate vegan code. But it's not "vegan" soup. It's just really good soup. I mean, I eat apples. I don't eat "vegan" apples. Can we just enjoy good soup without labeling it things? Please? Yes? Thanks. Friends still? Cool.
Now if you'll excuse me, there's a fast car on the internet that desperately needs me to watch it go fast.