Additional HERSHEY'S Milk Chocolate Chips, for garnish
Preheat oven to 350 degrees. Brush bottom and side of crust with egg yolk to seal crust. Place crust on baking sheet and bake 5 minutes.
Blend remaining whole egg, pumpkin, sweetened condensed milk and pumpkin pie spice in large bowl. Stir in 1/2 cup milk chocolate chips; pour into crust.
Place remaining 1/4 cup chips in a small microwave-safe bowl. Microwave at 50% for 30 seconds; stir. If necessary, microwave for an additional 10 seconds at a time, stirring after each heating, until chips are melted and smooth when stirred. Drizzle melted chocolate over pie in a decorative pattern.
Bake on baking sheet for 50 to 55 minutes or until wooden pick inserted into center of pie comes out clean. Cool 1 hour. Serve topped with whipped cream. Garnish with additional milk chocolate chips, if desired. Cover and refrigerate leftover pie.