In a large pot, heat 1 cup of the broth over medium heat. Add the onion and bell pepper and cook until softened, stirring occasionally, about 5 minutes. Add the garlic, minced chili, and mushrooms, then stir in the chili powder and tomato paste. Add the remaining ingredients, including the remaining cup of broth, and simmer, stirring occasionally, until the lentils are tender and the flavors are blended, about 50 minutes. Taste to adjust the seasonings, if needed, and serve hot.