Add the sliced mushrooms and water to the Instant Pot. Pressure cook on high for 10 minutes with a natural release.
While the mushroom broth is pressure cooking, dice the onion, mince the garlic and slice the carrots and celery.
When the mushroom broth is ready, strain the broth from the mushrooms and set aside.
Add the mushrooms, onion, olive oil and salt to the Instant Pot and set to sauté. Sauté the mushrooms and onions until browned.
Add the garlic, Italian seasoning and tomato paste to the Instant Pot. Continue cooking until the tomato paste has become dark red.
Add the sliced carrots, celery and lentils to the Instant Pot. Stir to coat the vegetables and lentils in tomato paste.
Add the mushroom broth to the Instant Pot and set the Instant Pot to pressure cook on high for 10 minutes with a natural release.
When the soup is done, add the fresh lemon juice and season with salt and pepper, to taste. Serve with crusty bread.
Notes
Don’t have an Instant Pot? Don’t worry. You can make this soup on the stove too. Follow the directions as described, but all the mushroom broth is simmer, covered, on the stove for an hour and for at least 30 minutes after adding the lentils.
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