Chocolate Mint Nanaimo Bars

Bahan-bahan (16 porsi)

• 2 cups graham cracker crumbs
• 1 cup coconut flakes
• 1 cup chopped walnuts (or pecans)
• ⅔ cup unsalted butter (melted)
• ½ cup granulated sugar
• ¼ cup unsweetened cocoa powder (plus 2 tablespoons)
• 1 egg
• 3 cups powdered sugar
• ½ cup unsalted butter
• 3 tablespoons milk
• 3 tablespoons custard powder
• 1 teaspoon mint extract
• green food coloring
• ¾ cup chocolate chips
• 2 teaspoons vegetable oil