Step 1: Heat oil in a pan over medium heat. Add chopped onion and chilies, cook for 2-3 minutes until soft.
Step 2: Stir in chopped garlic, add beans, and cook briefly, then mash the beans until creamy and set aside.
Step 3: Prepare pico de gallo: mix tomatoes, onion, chiles, cilantro, lime juice, and salt in a bowl.
Step 4: Assemble the tostada: spread beans on a shell, top with lettuce, and add pico de gallo.
Step 5: Finish with a dollop of cream, a sprinkle of queso fresco, and your preferred salsa. Enjoy!