Make your dough per the recipe instructions here. Or, cut ready made pie crust into rectangles and put in the fridge to chill while you make the filling. Preheat the oven to 350 degrees. For the filling, combine the cocoa powder, sugar, salt, and cream in a small saucepan over medium heat. Whisk until the mixture is smooth and sugar is dissolved. Remove from the heat, add the semi-sweet chips and stir until the morsels are combined and melted. Next, add the butter, and stir until fully incorporated. The mixture will firm up as it sits.
Next, assemble the pop tarts. Remove the dough from the fridge. Place a heaping tbsp in the middle of half of the pastries. Place another pastry on top of the filling, and crimp the sides together either with your fingers or a fork.
Brush each pastry with a little egg wash and prick the top of the pastries with a fork a few times. Bake for 20-25 minutes until golden brown.
While the pastries are baking, make your frosting. In a small saucepan, combine the half and half, butter, and sugar. Bring to a boil, then remove from the heat. Add in the chocolate chips and the peppermint extract. Stir until combined.
When the pastries are done, allow to cool slightly and then frost them. Sprinkle the top of each pastry with crushed candy canes. Allow to cool completely before eating. The frosting will set and the filling will cool. Store in an airtight container for up to 3 days.