How to Make It
Preheat the oven to 350° and line a 12-cup muffin pan with paper liners. In a bowl, whisk the flour, baking powder, baking soda and salt. In a large bowl, whisk the cocoa powder and chocolate chips with the boiling water until smooth. Add the sugar, sour cream, canola oil, eggs and vanilla; whisk until no streaks remain. Whisk in the dry ingredients until incorporated.
Fill the prepared muffin cups with the batter and bake for about 20 minutes, until a toothpick inserted in the center of the cupcakes comes out clean. Transfer the cupcakes to a rack and let cool completely.
In a heatproof bowl set over a saucepan of simmering water (the bottom of the bowl shouldn't touch the water), whisk the egg whites with the sugar and cream of tartar until the sugar has dissolved, about 3 minutes. Remove from the heat. Using a handheld electric mixer, beat the whites at high speed until stiff peaks form, about 6 minutes. Beat in the vanilla.
Transfer the meringue frosting to a piping bag fitted with a large round pastry tip and frost the cupcakes.