1. Remove top oven rack. Preheat broiler. Line oven rack with foil. Place bread slices in single layer on prepared rack. Replace rack; broil 1 minute or until bread is toasted; flip and broil about 20 seconds more. Remove and repeat with remaining bread slices. Reduce oven temperature to 225°F.
2. Top each toase slice with 1 slice white cheese. Cut 4 rounds out of each cheese-covered toast with 1-1/2-inch round cookie cutter; discard scraps.
3. Cut 4 rounds out of each slice of yellow cheese using same cookie cutter. Cut rounds into shapes to resemble the eight phases of the moon: crescents, halves, three-quarters and full moon. Place shapes on top of toasted white cheese rounds. (Leave some plain to represent the new moon.)
4. Place rounds on a baking sheet; bake 10 minutes or just until cheese is melted.