Spread a small amount of the butter on one side of each tortilla. Place one tortilla, butter side down, on a warm griddle. Top the tortilla with 1/4 of the cheese. Add some fresh spinach leaves & half of the corn salsa. Top with another 1/4 of the cheese & then top with another tortilla, butter side facing up. Cook over medium heat 1-2 minutes, or until the tortilla is golden brown, flip, and continue to cook until both sides are golden brown & the cheese is melted.