Bottom Layer: In a small saucepan, combine 1/2 cup butter and cocoa powder. Over low heat, mix until will blended.
Remove from heat and add 1/2 cup powdered sugar, egg and vanilla.
Stir in graham crackers and mix well.
Press graham cracker mixture into 9/13 glass or metal pan. (If you would like them thicker you can make in 8x8)
Middle Layer: Melt 1/2 cup butter. In a mixing bowl, mix together butter and creme de menthe on low speed for 2-3 minutes. Gradually add 3 cups powdered sugar and mix until smooth, about 3-4 minutes.
Spread over graham cracker mixture and chill in refrigerator for 1 hour.
Top Layer: In a small saucepan, combine 1/4 cup butter and chocolate chips. Stir over low heat until melted.
Spread over creme de menthe mixture.
Chill for 1 to 2 hours.
Store in refrigerator.