In a large Dutch oven or heavy-bottom saucepan (do not use a non-stick pan), heat 1 tablespoon of olive oil over medium-low heat. Have a cup of water nearby. Add the mushrooms and brown for 5 minutes, increasing the heat if needed. If bits of mushroom stick to the bottom of the pan and start browning, periodically add a splash of water and use a spatula to scrape up the brown bits and stir them into the mushrooms.
Once the mushrooms are browned, turn the heat to low and add the remaining olive oil. Add the onions along with a pinch of salt and cook for 2 minutes, stirring. Turn the heat up to medium and add the celery and bell peppers. Cook for an additional 5 minutes, stirring, then add the tomato paste. Let the tomato paste cook for 3-5 minutes, stirring only occasionally, so that it forms a brown glaze on the bottom of the pan along with the vegetables. Splash water into the pan a few times when the glaze forms, stirring it back into the vegetables.
Stir in the garlic, cumin, and chili powder, cooking for 1 minute. Add the diced tomatoes, chipotle chilis, adobo sauce, and beans. Turn the heat to medium-high and bring the ingredients to a simmer, then turn the heat down to low and cover. Cook for at least 30 minutes or up to one hour.
Serve hot with optional accompaniments. Leftovers will keep in an airtight container in the refrigerator for up to 4 days, or frozen for up to 3 months (I like freezing it in individual portions).
Other mushrooms may be substituted for the shiitakes. You can use all pinto or all black beans; I just like having a mix.The glazing/deglazing steps might seem cumbersome, but they add tons of flavor to the chili! Browning the ingredients along with the added mushrooms creates a depth and savoriness that’s often lacking in vegetarian chilis.Since I've tagged this as a vegan recipe, please note that not all of the suggested accompaniments are vegan. Recipe Pairings: I recommend serving this chili with my buttermilk biscuits or pretzel buns!