Cake:

• 1 3/4 cup all-purpose flour
• 2 cups white sugar
• 3/4 cup unsweetened Dutch-process cocoa powder
• 2 tsp baking soda
• 1 tsp baking powder
• 1 tsp salt
• 1 cup buttermilk, half and half, or whole milk
• 1/2 cup vegetable oil
• 2 large eggs
• 1 tsp vanilla extract
• 1 cup hot brewed coffee

Pudding Filling:

• 2 tablespoons unsweetened Dutch-process cocoa powder
• 1 cup boiling water or hot brewed coffee
• 6 Tbsp sugar
• 1 ounce bittersweet chocolate, chopped
• 1/4 tsp salt
• 2 Tbsp cornstarch
• 2 Tbsp cold water
• 1 tsp vanilla
• 1 Tbsp butter

Frosting:

• 3/4 cup unsalted butter
• 12 ounces semisweet chocolate, chopped finely
• 1/2 cup hot water
• 1 tablespoon corn syrup
• 1 tablespoon vanilla