Chocolate Mint Nanaimo Bars

Ingredients

• 1 3/4 cups HERSHEY'S CHIPITS Mint Chocolate Chips, divided (425 mL)
• 1/2 cup butter (125 mL)
• 1 1/4 cups graham wafer crumbs (300 mL)
• 1 cup flaked coconut (250 mL)
• 1/2 cup finely chopped walnuts or pecans (125 mL)
• 2 cups icing sugar (500 mL)
• 1/4 cup softened butter (50 mL)
• 3 tbsps milk (45 mL)
• 2 tbsps custard powder (30 mL)
• 1 tsp mint extract (5 mL)
• green food coloring
• 2 tsps vegetable oil (10 mL)