Prepare pudding first. In a small saucepan, add milk, sugar, dark chocolate, starch, and coffee. Bring to a boil, stirring constantly, until thick.
Remove from heat. Mix in vanilla and salt.
Pour pudding into a bowl and cover tightly with plastic wrap. Chill in refrigerator for at least 1 hour.
While the pudding is chilling, make the cupcakes.
Preheat oven to 350°F.
Line two cupcake pans with liners and set aside.
In a large bowl, sift flour, sugar, cocoa, baking soda, baking powder, and salt.
In a medium bowl, whisk melted butter, oil, buttermilk coffee, eggs, and vanilla.
Add wet ingredients to dry. Mix until combined.
Divide batter into cupcake pan filling each section ⅔ of the full.
Bake 20-22 minutes, or until a toothpick inserted in the center comes out clean.
To make the Swiss meringue, whisk egg whites, sugar, and cream of tartar in a double boiler over medium-low heat. Continue whisking until sugar completely dissolves, about 3-5 minutes.
Transfer to the bowl of an electric mixer fitted with the whisk attachment. Whisk on high for 7-10 minutes, until the meringue has reached firm peaks.
Make the whipped cream by beating cold heavy cream with powdered sugar until the cream reaches stiff peaks.