Step 1

Adjust oven racks to upper-middle and lower-middle positions, place rimmed baking sheet on upper rack, and heat oven to 450 degrees. Toss coleslaw mix with 3 tablespoons jalapeño brine in bowl and season with salt and pepper to taste; set aside for serving. In second bowl, whisk sour cream and 2 tablespoons lime juice together; set aside for serving.

Step 2

Combine chorizo, corn, and oil together in third bowl and spread in single layer on hot sheet. Cook until browned, about 15 minutes.

Step 3

While the chorizo and corn are roasting, combine beans, broth, jalapeños, and remaining 1 tablespoon brine in clean bowl and microwave until warm, about 2 minutes. Mash beans with potato masher until spreadable, season with salt and pepper to taste, and spread evenly over tostadas. During final 5 minutes of roasting chorizo, place tostadas directly on lower oven rack to warm through.

Step 4

Remove sheet from oven, transfer chorizo-corn mixture to large bowl, and stir in tomatoes and remaining 1 tablespoon lime juice. Divide mixture evenly among tostadas. Top tostadas with slaw, lime crema, queso fresco, and cilantro. Serve.