Lentil soup does not need to be made in an Instant Pot, as you can whip up a good lentil soup in less than 40 minutes on the stove. Recipes for Instant Pot lentil soup will say the process takes eight minutes, but once you’ve sautéed your vegetables (in batches, as to not overcrowd), brought your pot up to pressure, cooked for “only eight minutes” and then vented the steam, you’ve still waited over half an hour to eat. So if you’re going to bother involving an Instant Pot in making lentil soup, you’ve got to make those minutes you’re saving count for something. Say, for example, caramelized onions.
If you’ve never attempted them before, you should know that making caramelized onions in an Instant Pot sucks. Since it’s a closed chamber, there is nowhere for the evaporated liquid to escape to, meaning that once you’ve pressure cooked them you need to continue cooking them using the Instant Pot’s sauté function. (This is something you’re going to see me bring up in every Instant Pot recipe I ever write: If you’re going to brown meat, reduce liquid, or anything else that requires high heat, using the stove will give you better results and save time.) Pressure cooking is going to yield a bunch of not-quite-caramelized onion pieces floating in a sweet golden broth—a broth that just so happens to be perfect for making soup. Instead of boiling all that liquid off, I strained it, pressing every last drop out of the onion pulp before putting it into a skillet to continue caramelizing while I worked on making the rest of the soup. By the time I was ready to seal the Instant Pot for the second time, the onions had been fried up nicely to a deep amber, with flecks of dark brown.
I chose to cook the caramelized onion paste on high specifically to get those little almost-burnt specks, because they’re essential in my favorite caramelized onion dish: mujaddara. It’s a Middle Eastern dish made of spiced lentils and rice, smothered in tons of fried onions and maybe a dab of tangy yogurt. It inspired the spices I used in this soup, which ended up being very much like a cross between mujaddara and French onion soup. It’s completely vegan, too, if you decide not to top it with the yogurt-dolloped bread. That part is optional, and I don’t think the soup suffers one bit without it, but some people think that soup isn’t actually a meal if there’s no bread involved, and I aim to please.
I must stress this: When it comes to soup, you need to taste for seasoning right before you serve it, and that seasoning is entirely in your hands. My husband added a bit more salt to his bowl; I added another few drops of vinegar to mine. Soup recipes are really just guidelines—once you get to the end, tweak as necessary until you’ve created the soup of your dreams. You deserve nothing less than the best soup.
Instant Pot French Onion Lentil Soup
- 4 lbs. yellow onions
- 1/2 tsp. baking soda
- 1/4 cup water + 5 cups hot water
- Olive oil, for sautéing
- 3 cloves garlic
- 1 Tbsp. + 1 tsp. red miso paste
- 1 1/2 tsp. allspice
- 1 1/2 tsp. cumin
- 1 tsp. coriander
- 2 tsp. kosher salt
- 1 lb. brown lentils, well rinsed
- 1 Tbsp. balsamic vinegar
- Miniature naan or pita chips, optional
- Greek yogurt, optional
- Chopped parsley, optional
Take four big onions out of your pile of onions and put them aside. These will be sauteed later instead of being caramelized, thus giving you two different onion flavors and textures in your finished soup.
Coat the bottom of the Instant Pot with olive oil, then turn on the sauté function. French cut the onions, throwing them in the pot as you go, tossing in the baking soda after the first few are in the pot and giving them a good stir now and again—it takes a while to get onions going, so by cooking while you’re prepping, you give yourself a nice head start on things. Once all the onions are in the pot, add 1/4 cup of water, set the vale to “seal,” and set the pot to cook on high for 15 minutes. It’s going to take about 25-30 minutes to get to pressure and cook.
When the timer beeps, manually vent the steam. Set a wire strainer over a mixing bowl, and set a cast iron or nonstick skillet over medium-high heat with a bit of olive oil coating the bottom to warm up. Ladle out the onions a bit at a time into the strainer, push them down with a wooden spoon to drain out all the liquid, and throw the onion solids in the hot pan. Keep on doing this, working quickly but not rushing, until the Instant Pot is empty (you don’t need to clean it). In the bowl, you should have 3-4 cups of golden onion broth, which you can set aside. In the pan, spread out the onions to help rapidly evaporate any extra liquid, giving them a good stir every minute or so, allowing them to caramelize and crisp while the rest of the soup is being assembled. If it looks like they’re burning, turn the heat down a bit, but keep them cooking. You want them to be hot when they go back into the Instant Pot.
Now, make the soup. Turn on the Instant Pot’s sauté function. French the remaining four onions and throw them into the pot with a big pinch of salt, then mince the garlic and throw that in. Add the cumin, coriander, and allspice, and continue cooking for about a minute so that the spices toast and become intensely fragrant. Add a small bit of the onion broth to deglaze the pan, scraping up all the brown bits from the bottom, and then stir in the miso paste until dissolved. Pour in the remainder of the onion broth, the salt, the hot water, and the lentils. Remove the caramelized onion paste from the stove and stir it into the Instant Pot, then close the lid. Turn off the sauté function; turn on the pressure cook function, and set for 8 minutes on high.
When the timer beeps, allow the Instant Pot to naturally release for three minutes before turning the vent to depressurize. Stir in the balsamic vinegar, then taste for seasonings, adding more salt/spice/miso/balsamic as you please.
Serve immediately with—if desired—naan or pita chips dolloped with Greek yogurt, chopped parsley, and freshly cracked black pepper.