01 - Cook bacon in a skillet over medium heat until evenly crisp. Transfer to paper towels to drain excess fat.
02 - Spread softened butter on one side of each bread slice.
03 - Arrange two bread slices, butter-side down, on a clean work surface.
04 - Top each bread slice with 2 slices cheddar, 1 slice Monterey Jack, crispy bacon, and jalapeño slices. If using, spread cream cheese on the inside of the remaining bread slices.
05 - Cover with remaining bread, buttered side facing up.
06 - Warm a large skillet or griddle over medium-low heat.
07 - Place sandwiches in skillet and grill for 3 to 4 minutes per side, pressing gently, until golden brown and cheese is melted.
08 - Remove from heat. Let rest briefly, slice, and serve immediately.