Heat a large skillet over medium-high heat and add the ground beef, breaking it into small crumbles as it browns.
Incorporate cumin, chili powder, garlic powder, salt, and pepper into the beef; cook until fully browned and drain excess fat.
Spread softened butter onto one side of each bread slice.
Apply chipotle mayonnaise to the non-buttered side of two bread slices.
Layer one slice of Monterey Jack cheese, half of the beef mixture, pickled jalapeƱos, red onions, and avocado slices onto the mayonnaise-covered side.
Place a second slice of cheese over the fillings and top with the remaining bread slice, buttered side facing outward.
Preheat a clean skillet or griddle over medium heat.
Place sandwiches in the skillet and toast for 3 to 4 minutes per side, or until the bread is golden brown and the cheese is completely melted.
Remove from heat, slice diagonally, and serve immediately.