Preparation Preheat oven to 300°F. Fry chorizo in medium skillet over medium-high heat until meat is cooked through and fat is rendered, about 10 minutes. Drain off all fat from skillet. Add beans to chorizo and stir until heated through, about 2 minutes. Remove from heat; cover to keep warm. Heat 2 tablespoons oil in heavy large nonstick skillet over medium-high heat. Add onion and sauté until onion is soft, about 4 minutes. Arrange tostadas on baking sheet. Spread 1/3 cup bean-chorizo mixture on each tostada. Top with onion. Place in oven to keep warm. Heat remaining 2 tablespoons oil in same skillet over high heat. Drop in eggs 1 at a time. Fry over medium-high heat until whites are firm but yolks are still tender, about 1 minute per side. Using metal spatula, place 1 egg on each tostada; top with salsa, avocado, and cheese.
Preparation Preheat oven to 300°F. Fry chorizo in medium skillet over medium-high heat until meat is cooked through and fat is rendered, about 10 minutes. Drain off all fat from skillet. Add beans to chorizo and stir until heated through, about 2 minutes. Remove from heat; cover to keep warm. Heat 2 tablespoons oil in heavy large nonstick skillet over medium-high heat. Add onion and sauté until onion is soft, about 4 minutes. Arrange tostadas on baking sheet. Spread 1/3 cup bean-chorizo mixture on each tostada. Top with onion. Place in oven to keep warm. Heat remaining 2 tablespoons oil in same skillet over high heat. Drop in eggs 1 at a time. Fry over medium-high heat until whites are firm but yolks are still tender, about 1 minute per side. Using metal spatula, place 1 egg on each tostada; top with salsa, avocado, and cheese.