Potage St. Germain {Minted Pea and Lettuce Soup}

First off, thanks to everyone for the kind, supportive, and encouraging notes regarding my last post (wherein I was offered a cookbook deal only to find after a month of tedious negotiations that it was a no-go). I never thought I’d receive so many kudos for not getting a book deal (even from my parents). So, thanks!
For this, you all deserve dessert. Instead, I’m giving you soup. Soup made with lettuce, at that. I’m sorry. Have some soup, preferably eaten alongside these carrots and a hunk of bread, and dessert will be up shortly. Promise.
I’ve intended to post this soup every spring since I started my blog. I discovered it whilst on a low-carb diet when I lived in Italy (don’t worry, I’ve more than made up for it by now). I’ve had the serious hots for sugar and sweets since I was little, so, as unhealthy as I now believe high-protein diets to be, it helped me appreciate how naturally sweet vegetables are. Including peas. 
Potage St. Germain came to my carb-starved rescue. I seem to like all things named St. Germain (including the elderflower liqueur, the Parisian church, and the nu jazz musician) and this soup was no exception. I found the recipe on Epicurious, and it consisted of peas cooked and pureed with leeks, lettuce, and mint. The thought of putting lettuce in a soup perplexed me, but, hey, it was low-carb after all, so I went with it (and wrote down how many carbs it contained in the little notebook that ruled my life). The result was a sweet, creamy, and fresh-tasting bowl of green loveliness. That summer was heinously hot, so I was pleased to find that it tasted equally good cold (especially since gelato, fruit, and cocktails were all off the menu).
Thankfully, Potage St. Germain doesn’t only taste good when one’s body is famished for sugar. Peas and leeks make a sweet and creamy base; lettuce beefs up the soup while letting the flavor of fresh sweet peas (or frozen – I won’t tell) come through, and a handful of mint added at the end brightens things up. 
I’ve made a few changes to the recipe over the years. The original calls for chicken stock, but I keep it vegetarian by making a quick stock from the vegetable trimmings (pea pods, leek greens, plus a bit of carrot, potato, and fennel). I thought the soup could use a bit more body, so I added a potato there as well. And lately I seem to want lemon juice in and on everything, so I add a good squeeze at the end. 
I like this soup best just warm; when piping hot, the mint flavor tastes a bit off to me. I swirl in a bit of tangy crème fraîche (which I don’t recommend skipping as it really rounds out the flavors, though you can use sour cream or plain, whole milk yogurt in a pinch). Croutons make a crispy garnish; the ones shown here were made from Bread Srsly‘s gluten-free sourdough.
Whether you’re counting calories or not, you’re certain to find nourishment in this springy soup.
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Potage St. Germain {Minted Pea and Lettuce Soup}
Adapted from Epicurious
I won’t lie; I use a combination of fresh and frozen peas for this soup. Be sure you’re buying English peas, the kind designed for shelling. As you prep your soup ingredients, add the trimmings to the pot. For the best color and flavor, let the soup cool to room temperature before adding the mint and lemon juice and pureeing. Reheat gently to keep the fresh flavor of the mint and lemon. I like this soup best barely warm, swirled with crème fraîche, a handful of fresh peas, and some crunchy croutons.
Makes 6-8 servings
For the stock:
green trimmings from 1 leek, rinsed well and chopped (from the leeks below)
2 cups pea pods (from the peas below)
1 carrot, roughly chopped
1 celery stalk or half a small fennel bulb, roughly chopped
1 yellow or russet potato, scrubbed and roughly chopped, plus the peels from the potato below
8 cups water

For the soup:
white and light green parts of 2 large leeks, sliced
2 tablespoons butter
1 large yellow potato, peeled and diced
1 teaspoon fine sea or kosher salt
4 cups shelled fresh peas (from about 4 pounds fresh peas) or 2 (10 ounce) bags frozen peas
4 cups washed and chopped lettuce (preferably romaine or little gems)
1/2 cup mint leaves
juice of 1 lemon, or to taste

For serving (optional):
1/2 cup crème fraîche
mint leaves
fresh or blanched peas
Make the stock:
Combine all of the stock ingredients in a large pot. Bring to a boil, reduce the heat to medium, and simmer, partly covered, 20-30 minutes. Strain and reserve the stock. (If you’re like us, pull out all the carrots and potato chunks and mash them up with a knob of butter and some salt for a pre-soup snack.)
Make the soup:
Meanwhile, place the sliced leeks in a large bowl and fill with cool tap water. Swish the leeks occasionally to remove any sand from between their layers, which will sink to the bottom. Melt the butter in a large saucepan over medium heat. Lift the leeks out of the water, give them a shake, and add them to the pot along with the diced potato. Saute, stirring frequently, until the leeks are tender, 10 minutes, reducing the heat if the leeks begin to brown at all. Add 6 cups of the stock and the salt, bring to a simmer, and cook until the potatoes are tender, 10 minutes or so. Add the peas, and simmer 5 minutes. Add the lettuce, and bring to a simmer for 1 minute. Remove from heat and let cool to room temperature. 
Add the mint leaves, and puree the soup with a hand blender or in batches in a blender. Add the lemon juice. Taste, adjusting the salt or lemon if needed, adding more stock or water to thin the soup if you like.
To serve, heat the soup gently, stirring frequently, over a medium flame until just warm. Ladle into bowls, and swirl with crème fraîche, peas, a few mint leaves, and a handful of croutons. 
The soup is best shortly after being made when the color and flavor are bright, but it will keep, refrigerated, for up to 5 days.

23 thoughts on “Potage St. Germain {Minted Pea and Lettuce Soup}”

  1. This soup looks absolutely divine! I have to admit I've never tried lettuce in soup, but I trust your judgement enough to give it a try. Especially since we sound so similar with the sweet tooth and loving elderflower liqueur. ;)

    Stunning photos!

    1. Hi Jennifer! Thanks for the kind words! Yes, I think we have similar tastes based on the fact that I want to make everything ever from your beautiful blog. :) I was skeptical about the lettuce, too, but it works surprisingly well!

  2. That sucks so hard about the book – so sorry to hear! I can only imagine how much prep work you had to do, but at another time hopefully everything will work out! I'll be first in line for THAT book. Also, this soup is almost too perfect for Spring. Love the colour!

  3. Ah, forget dessert–soup is far superior! Especially when it's as green and vibrant as this one. Cooked lettuce is always an interesting thing to try to explain to people who've never had it before, isn't it? I especially like saving the ends of heads (well washed) for vegetable stock.

    1. Aw, thanks, Eileen! Such a good tip on the stock. I've been seeing recipes for grilled romaine lately, so hopefully there is a future when cooking lettuce isn't considered weird and freakish!

    1. Thank you, Sue! Yes, I love fresh peas, but when they get blended up like this, frozen can be the way to go (unless you have a garden full of peas that you need to use up).

  4. I'm so intrigued by the idea of putting lettuce in soup! So intrigued, that I have to make this soon just to see what it is like! It is so perfect for spring and the warmer weather that is coming. I love your photo of the lettuce, it is so beautiful :)

  5. What a gorgeous green soup. For as much as I like soup, I've never tried to make a green one before. I'm so inspired now! Thank you for sharing!

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