Session 1: Prep the Cupcakes Heat the oven to 350 degrees. Generously coat the wells of a 12-cup muffin pan with oil or butter.
In a small bowl, whisk together the cocoa powder and hot water until the cocoa has dissolved. In a medium-size bowl, stir together the flour, baking powder, and salt. In another small bowl or glass measuring cup, stir together the milk and vanilla.
In a large bowl, use a mixer set on medium speed to beat together the butter and sugar until smooth, scraping the sides as needed, about 2 minutes. Increase the mixer's speed to high and add the eggs, one at a time, beating well between each addition until a thick, creamy batter has formed, about 3 minutes.
Add one third of the flour mixture to the egg mixture and beat at low speed until the flour has disappeared. Pour in half the milk mixture and continue beating until well blended. Repeat the process, alternating between the milk and flour mixtures and beating between each addition until evenly blended.
Pour half the batter into a separate bowl. Quickly whisk the cocoa mixture, then add it to one of the bowls of batter and stir until evenly blended.
Add 1/4 cup of the chocolate batter to six of the muffin wells. Divide the vanilla batter among the remaining six wells. Transfer the pan to the oven and bake until the cupcakes have begun to pull away from the sides of the pan, about 15 to 20 minutes. Transfer the pan to a wire rack and let the cupcakes cool for 10 to 15 minutes. Gently loosen the cupcakes from the pan and transfer them to a platter to cool completely. Reserve the muffin pan and remove the ice cream from the freezer to soften.
Slice three vanilla and three chocolate cupcakes in half crosswise (save the rest for another dessert). Reassemble them, swapping the tops and bottoms so that each cupcake has one vanilla and one chocolate half. Return the cupcakes to the muffin pan.
Remove the top from one of the cupcakes and add a 1-inch layer of ice cream (the well should be nearly full). Press the top back into place and repeat with the remaining cupcakes. Cover the pan with plastic wrap and freeze the desserts until solid, about 3 hours.
Session 2: Bake and Serve About 15 minutes before serving, heat the oven to 450 degrees and make the meringue. In a medium-size bowl, use a mixer set on medium speed to beat the egg whites until frothy, about 2 minutes. Add the cream of tartar and continue to beat until soft peaks form, about 2 minutes more. Slowly blend in the sugar, then increase the speed of the mixer to medium-high and beat the eggs until they are stiff and glossy as shown at left, about 2 minutes.
Run a knife around the perimeter of the cupcakes to loosen them from the pan. Transfer them to a waxed paperlined cookie sheet. Working quickly, add a large dollop of meringue to the top of each cupcake, dividing it evenly among them. Use a butter knife to spread the meringue over each dessert, covering it entirely. Use the back of a spoon to form small peaks on the surface of the meringue.
Bake the desserts until the meringue is lightly browned, about 6 minutes. Use a spatula to transfer each Baked Alaska to an individual plate and serve immediately. Makes 6.
