Sauté and Combine: Select the Instant Pot sauté button and add the oil. When the oil is hot and shimmering, add the chorizo. Cook, breaking the sausage up, for about 3 minutes. Add the onion and garlic and continue cooking and stirring for 3 minutes longer, or until the chorizo is well browned. Add the carrots, celery, chicken stock, tomatoes, lentils, bay leaf, pepper, and 1 teaspoon of kosher salt (if using salted broth, wait until later to taste and add salt). 

Pressure Cook: Lock the lid in place and ensure the steam release valve is set on sealing. Select high pressure (either the manual or pressure cook button) and set the timer for 7 minutes. It will take about 15 minutes to increase pressure. When the time is up, let the pressure come down naturally for about 15 minutes, and then release the remaining pressure.  

Finish the Dish and Serve: If desired, add chopped spinach and change to the sauté function. Cook just until the spinach is wilted. Taste and adjust seasonings, as needed. Serve with a garnish of chopped cilantro or parsley.