Spread the garlic butter on the outer sides of the tortillas.
Spread the cheeses on the inner side of 1/2 of each tortilla, then fold to form a half-moon.
Grill the tortillas covered over medium heat until the first side is golden brown. Flip the tortillas and grill the other side until the cheese has completely melted.
Cut into wedges, plate and serve with sour cream and salsa.