
Combine cream cheese, jalapeños, garlic powder, and parmesan cheese in a small bowl. Mix well.
Spread jalapeño filling over 2 of the slices of bread. Top with cheddar cheese and remaining slice of bread.
Spread mayonnaise over the outside of each slice of bread.
Preheat a small skillet over low heat. Place mayonnaise side down in the skillet.
Grill until golden, about 4-5 minutes. Flip and grill the other side until golden.