1 ripe avocado, pitted and peeled
1 cup unflavored soy or almond milk
1 tablespoon lime juice
1/2 teaspoon salt, or more to taste
Make the chickpea chorizo:Place the chickpeas and walnuts into the bowl of a food processor fitted with an S-blade. Pulse 4 or 5 times, just until the chickpeas are chopped and crumbly, being careful not to overdo it.
Coat the bottom of a medium skillet with oil and place it over medium heat. When the oil is hot, add the onion and sauté until soft and translucent, about 5 minutes. Add the garlic and sauté about 1 minute more, until very fragrant. Add the chickpea mixture, paprika, cumin, ancho chile powder, thyme, cinnamon, cayenne, black pepper, cloves, and 1/4 teaspoon of salt to the skillet. Gently flip a few times to incorporate the spices into the mixture. Cook, flipping occasionally, for about 5 minutes, until the mixture dries out a bit and begins to crisp in spots. Add vinegar and flip a few more times to incorporate. Remove from heat and season with additional salt and cayenne pepper if desired.
Make the shells:Preheat the oven to 400°F. Lightly spray both sides of the tortillas with oil or cooking spray, then place them in the over, arranging them flat, directly on the oven rack. Bake until they begin to brown and crisp, about 8 minutes.
Make the avocado crema:While the shells bake, place all ingredients into a blender and blend until smooth. Taste test and season with additional salt if desired.
Assemble the tostadas:Divide the chickpea chorizo among the shells and top with lettuce, tomato and avocado crema. Serve.