Place a pot on a burner over medium heat. Add the mushrooms to the dry pot and cook for 5–7 minutes until they release excess water. Cook for an additional 5 minutes until lightly browned. Season with salt and pepper.
Add the 1 tablespoon extra virgin olive oil to the pot of mushrooms along with the diced onions. Cook for 5–7 minutes.
Add the thyme, garlic, and Calabrian chili peppers. Cook for 1 minute until fragrant. Add tomato paste, if using, and cook for 1 minute.
Cook the beans and pasta:
Add the beans, tomatoes, and 4 cups water. Bring to a boil and season liberally with salt. Once boiling, add the orzo. Reduce heat to a low bowl (medium to medium-high, depending on your stove). Simmer, occasionally stirring, for 8–12 minutes until the orzo is al dente. Taste and season.
Finish the beans:
Add the chopped basil and lemon juice to the pot. Turn off the heat.
To serve:
Divide the cooked beans and pasta between bowls. Serve with black pepper and more fresh basil, if you like.