Preheat oven to 325 degrees F. Lightly coat twelve 2-1/2-inch muffin cups with cooking spray; set aside. For crust, in a small saucepan melt 1/3 cup butter over medium heat; remove from heat. Stir in 1/4 cup sugar. Stir in crushed graham crackers until combined. Spoon about 2 rounded tablespoons of the mixture into each prepared muffin cup. Press evenly onto the bottoms and 1 to 1-1/2 inches up the sides of the cups. Bake for 5 minutes; remove from oven.
Meanwhile, for filling, in a medium mixing bowl combine 1/2 cup sugar and egg. Beat with an electric mixer on medium speed about 2 minutes or until pale yellow and thickened. In a small bowl stir together flour and cocoa powder. Add flour mixture to egg mixture, beating just until smooth. Fold in coconut and 1/4 cup melted butter. Spoon filling evenly into crust-lined muffin cups.
Bake for 15 to 20 minutes more or until filling is slightly puffed and set. Cool in muffin cups on a wire rack for 5 minutes. Carefully remove pies from muffin cups; cool completely on wire rack.
Before serving, preheat broiler. Place pies on a large baking sheet. Top each pie with a marshmallow half. Broil 5 to 6 inches from the heat for 30 to 40 seconds or until marshmallows are puffed and golden. Serve immediately.