Preheat the oven to 375°F (190°C). Place the tostada shells on a baking sheet and warm them in the oven for about 5 minutes, or until they are crisp.

In a small saucepan, heat the refried beans over medium heat until warm and spreadable, stirring occasionally.

Prepare the guacamole: In a bowl, mash the avocados until smooth. Mix in the diced red onion, chopped cilantro, lime juice, garlic powder, salt, and black pepper. Adjust seasoning to taste.

Assemble the tostadas: Spread a layer of warm refried beans onto each tostada shell.

Top the beans with shredded chicken, ensuring an even distribution across all tostadas.

Add a dollop of guacamole on top of the chicken for each tostada.

Sprinkle shredded cheese over the guacamole layer. Optionally, place the tostadas back in the oven for 2-3 minutes to melt the cheese slightly.

Finish with shredded lettuce, diced tomatoes, and a drizzle of sour cream or hot sauce, if desired.

Serve immediately and enjoy your Chicken Guacamole and Bean Tostadas!