Preheat oven to 400°F. Press pie crust into a 9” pie plate as directed. Chill for 10 minutes in the freezer or 30 minutes in the refrigerator, then poke it several times all over the bottom and sides with a fork. Bake for 8-10 minutes, until slightly puffed and no longer glossy. Cool completely before filling.

Whisk sugar, salt, cocoa powder, cornstarch, and milk in a medium saucepan, then switch to a wooden spoon or heat-safe spatula. Cook over low heat until thickened, stirring constantly, about 5-8 minutes. Be sure to get in the corners of the pan when you're stirring as the solids can get stuck there. Remove from heat and stir in vanilla and chocolate chips; stir until chocolate is completely melted. Pour into prepared crust. Cool at room temperature, then cover tightly with plastic wrap and chill 4 hours or overnight.

Before serving, make the whipped cream. Beat cold heavy whipping cream in a cold bowl with cold beaters until stiff peaks form, adding powdered sugar slowly during the mixing. Spread on the pie and garnish with mini chocolate chips, if desired.