Combine ingredients for the black bean dip in a food processor the process until smooth, scraping down sides as needed. Taste and add more salt and pepper if necessary. Smooth into the bottom of a 9-inch pie pan and place into the refrigerator while making Sweet Corn Guacamole.
Add avocados, lime juice, garlic, salt and pepper to a large bowl then mash until smooth. Taste and add more salt and pepper if necessary. Fold in thawed sweet corn and cilantro then smooth on top of the black bean dip. Sprinkle on chopped tomatoes and crumbled Cotija cheese and serve with tortilla chips and crudite.