Pie crust: In a food processor, add flour, cocoa powder, sugar and salt and pulse to combine. Add cold butter, cut into 1 inch pieces, and pulse until you have pea size chunks of butter. Add vinegar and water and pulse until the dough starts to come together. Place on floured surface and knead until all flour is incorporated, it won’t be smooth. Wrap in plastic wrap and refrigerate for at least 30 minutes.
Roll the dough out and place in a pie pan, poke with a fork all over and let it chill while the oven preheats to 425º. Place a piece of parchment paper or foil covering the pie crust and add pie weights or dried beans etc. Bake for 15 minutes, remove the pie weights and parchment and continue to bake for 2-3 minutes until it is golden brown and looks dry. Cool completely.
Ganache: Place the cream in a saucepan and bring to a boil. Pour the hot cream over the chopped chocolate and let it sit for 15 seconds, then gently stir until it is smooth. Pour the warm ganache into the cooled pie crust and spread it evenly over the bottom. Let this cool for 15 minutes before adding the pie filling.
Chocolate filling: In a saucepan, heat the milk and cream over medium heat until it simmers. Add chocolate and stir until melted. In a medium bowl, whisk the sugar, cornstarch and salt together then whisk in the egg yolks. Pour about a quarter of the hot chocolate into the egg mixture a tablespoon or so at a time, whisking constantly. Add the egg mixture to the saucepan and cook over medium heat stirring constantly until it is very thick and large bubbles form. 3-5 minutes.
Remove from the heat and stir in butter and vanilla. Pour on top of the ganache in the pie crust and cover with plastic wrap, with the wrap pressing directly onto the warm surface. Place in the refrigerator for at least 45 minutes.
Cherry Topping: In a saucepan, add cherries and lemon juice. In a small bowl stir surge and cornstarch together and add to the cherry mixture. Cook over medium heat, stirring frequently until the cherries are soft, about 5 minutes. Add vanilla and bitters and spread out onto a cookie sheet to cool. Once cool, remove the plastic wrap from the chocolate pie filling and add the cherry mixture on top, spreading it evenly. Refrigerate until ready to serve.
Serve with whipped cream. (to make whipped cream combine a cup of heavy cream with 1/4 cup sugar and a teaspoon of vanilla and beat until medium peaks form.)