Prepare the chocolate filling base: In a heatproof bowl, melt the chocolate chips and butter together. You can do this over a double boiler or in short microwave bursts, stirring every 20–30 seconds until smooth and glossy. Once melted, let it cool slightly so it doesn’t cook the eggs later.

Mix the custard filling: In a separate bowl, whisk together the sugar and eggs until the mixture becomes pale, slightly thick, and well combined. Slowly pour in the melted chocolate mixture while whisking constantly so the eggs don’t scramble. Add vanilla extract and continue mixing until everything is silky and fully incorporated.

Fill the pie crust: Pour the chocolate filling into the pre-baked pie crust. Use a spatula to smooth the top so it spreads evenly all the way to the edges. Tap the pie gently on the counter to remove any air bubbles and ensure a smooth satin-like surface.

Chill until set: Place the pie in the refrigerator and chill for at least 4 hours, or until the filling is firm and set. For best results, chill overnight so the texture becomes rich, dense, and sliceable like the classic Marie Callender’s version.

Prepare whipped topping: In a mixing bowl, whip the heavy cream with powdered sugar and cocoa powder until soft peaks form. The texture should be light, fluffy, and stable enough to hold its shape when spread or piped.

Finish and serve: Spread or pipe the whipped cream over the chilled pie. Add chocolate shavings or curls on top for a bakery-style finish. Slice carefully with a warm knife for clean cuts and serve chilled for the best creamy texture.