Preheat oven to 350°F. Unroll pie crust and place it into pie plate. Chill until ready to fill.: As the oven warms you should notice a faint oven smell that signals it is reaching temperature, and the chilled crust will relax into the plate without shrinking; chilling the crust keeps the fat cold so the edges stay flaky. If the crust feels warm or tacky, return it to the refrigerator for ten to fifteen minutes, because a warm crust can slump during blind baking and result in a dense edge. A typical mistake is rushing this step, which can cause an uneven crust, so take the few extra minutes to keep everything cold.
Whisk butter and cocoa. Whisk in eggs. Add sugar, salt, vanilla, and flour and whisk until smooth. Gently whisk in milk. Stir in peppermint baking pieces.: Right away you will smell the chocolate lift as the butter and cocoa combine, giving a toasted cocoa aroma. Be mindful when adding the eggs to the warm butter; let the butter cool briefly or whisk briskly so the eggs do not scramble. The batter should become glossy as the sugar dissolves, and small streaks of air will settle out with a few quiet stirs. Fold in the peppermint pieces at the end to keep them intact; overmixing can pulverize them and make the filling streaked rather than dotted. One common error is not fully dissolving the sugar, which can leave a grainy texture, so whisk until smooth and check the bottom of the bowl for undissolved crystals.
Pour batter into prepared pie shell. Bake for 45-55 minutes until it’s just slightly jiggly in the center and no longer glossy on top. Cool completely before slicing and topping.: As the pie bakes you will see the edges set first, turning a matte, satiny sheen while the center retains a subtle wobble; listen for a very gentle popping of tiny bubbles near the surface, and expect a sweet, chocolatey perfume. The visual cue of losing the glossy top paired with a slight jiggle in the middle is your signal to remove it from the oven. If you bake until it is fully firm with no jiggle you risk a dry, rubbery texture, so err on the side of a tender center. Cooling is crucial, because the filling firms as it chills; slicing too soon will cause the filling to be overly soft and messy on the plate.
Serve with whipped cream or Cool Whip and crushed candy canes.: The final step is about contrast, and when you add a dollop of whipped cream you introduce a cool, airy note against the dense custard. The crushed candy cane provides a crunchy, minty counterpoint and a festive look. For best presentation, spoon the cream gently so you do not disturb the slice, and sprinkle crushed candy canes immediately before serving so they maintain their crispness. A typical misstep is over topping, which can overwhelm the delicate chocolate mint balance, so use garnish sparingly.
Store pie in refrigerator for up to 2 days or freeze for up to one month.: Once cooled, the pie will keep its texture in the refrigerator , but you should cover it loosely to prevent the whipped topping from absorbing fridge odors. If you plan to freeze, wrap the pie tightly in plastic and foil to protect it from freezer burn; thaw overnight in the refrigerator to maintain its creamy structure. A common mistake is storing the pie at room temperature for long periods, which can cause the filling to weep or develop an off texture, so refrigerate promptly for best results.