Place flour into a bowl with salt and diced butter and shortening. Using your hands, crumble and squish the fats into pea and marble sized pieces. Place into the freezer, and get ¼ cup of water, place ice cubes in it, and set aside.
After 10-15 minutes, remove flour/fat mixture from freezer, and using a fork slowly stir in the ice water until the dough starts coming together. Target consistency is slightly crumbly but able to be pinched together and hold. Pour mixture out onto a lightly floured surface and form into a disc. Wrap in plastic wrap and chill for at least 30 minutes to an hour.
Roll out pie crust to ¼ inch thick, place in pie pan, line with parchment and fill with pie weights and blind bake until edges are golden brown. Carefully remove pie weights and parchment and place back into oven, reduce heat to 375, and continue baking until entire crust is golden brown.
While the crust is baking, place the custard sugar, flour, cornstarch, and salt into a medium sized saucepan. Whisk together egg yolks and milk in a separate bowl until fully combined, and the slowly pour into flour mixture, whisking while pouring, until no lumps remain. Chop chocolate.
Prepare whipped cream by beating heavy cream, vanilla, and powdered sugar until stiff peaks form. Spread over chilled chocolate and top with mini chocolate chips. Best served after chilling prepared pie overnight, but will still taste amazing if served right after topped with the whipped cream.