Whether you want to layer tostadas with beans, meat and vegetables, or customize using your favorite ingredients, tostadas are incredibly flexible. We started with the mashed bean base that’s commonly enjoyed in Mexico, and added sweet potatoes and pineapple for a touch of sweetness.
Put the sweet potatoes in a large skillet and add enough water to cover; season with salt and pepper. Bring to a boil, reduce the heat to a simmer and cook until tender, 20 to 25 minutes. Drain and return to the skillet.
Meanwhile, mix the cabbage, 1 tablespoon lime juice and a pinch of salt in a small bowl; set aside. Toss 1 cup pineapple with the cilantro and 1 tablespoon lime juice in a small bowl; set aside. Puree the remaining 1 cup pineapple with 1 tablespoon lime juice, the garlic, chipotle and adobo sauce, cumin and 1/4 cup water in a blender until smooth. Stir the pineapple sauce into the sweet potatoes and cook over medium heat until warmed through, 3 to 4 minutes.
Put the black beans in a small saucepan, add 3 tablespoons water and warm over medium-high heat. Spread on the tostadas, then top with the sweet potatoes, pineapple salsa and cabbage. Drizzle with the crema.