Butter one side of each piece of bread, reserving 1 tsp. butter for later.
Assemble sandwich by spreading one piece of bread with cream cheese, then topping with pepper jack cheese, bacon, and sliced jalapeños.
In a small skillet or griddle, melt remaining 1 tsp. butter. Stir in panko crumbs and toast until golden brown.
Sprinkle toasted panko crumbs on sandwich, then top with second piece of bread.
Grill on each side 5-10 minutes or until golden brown.