Preheat oven to 350 F. Prepare 2 muffin tins by lightly greasing with oil (butter), spray with non-stick spray, or line with muffin liners.
Cupcake Preparation: In a large bowl, sift together flour, Rumford Baking Powder, cocoa powder, Clabber Girl Baking Soda, salt, and sugar. Make a well in the center of dry mix and add the eggs, milk, vegetable oil (canola), and vanilla. Whisk to combine. Add the boiling water and whisk until smooth. Batter will be quite thin but do not worry. Transfer the batter to a liquid measuring cup and divide evenly among the lined muffin cups. Bake for about 22 minutes, or until the cupcakes spring back when pressed gently with your finger. Cool on a rack.
Frosting Preparation:Melt the chocolate and butter over warm (not boiling) water. Transfer to the work bowl of a stand mixer or using a hand held beater whisk in the cream, vanilla, and salt together. Sift in the powdered sugar and cocoa powder mixing no higher than medium speed until smooth.
If you like, infuse your cupcakes with a chocolate center. Spoon about 1/3 of the frosting into a pastry bag, simply snip off the corner off of a small plastic baggie (leaving about a 1/4 inch opening). Using a small knife, poke a small hole in the center of the cupcake. Insert the tip of the pastry bag or cut corner of the small plastic baggie and squeeze slightly. With this generous filling, you will simply need to spread a thin glaze of frosting over the surface of the cupcake to cover. If you skip this step, spread a more generous amount of frosting over the cupcake top.