1. Preheat oven to 375*F. Line 36 muffin cups with paper liners.
2. In a large bowl, mix together the flour, sugar, cocoa, baking soda and 1 teaspoon salt. Make a well in the center and pour in the eggs, 1 cup milk, water, oil and 1 teaspoon vanilla. Mix well. Fill each muffin cup half-full of batter.
3. Bake in the preheated oven for 15 to 20 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow to cool.
4. Make filling: In a large bowl, beat butter and shortening together until smooth. Blend in confectioners' sugar and pinch of salt. Gradually beat in 3 tablespoons milk and 1 teaspoon vanilla. beat until light and fluffy. Fill a pastry bag with a small tip. Push tip through bottom of paper liner to fill each cupcake.
My Notes: Here is the EASIEST tip for filling the cupcakes. Take an APPLE CORER and use that to pull a cylindrical plug of cake out of each cupcake (once they've cooled). Save the plugs on the side while you pipe filling into each hole you've created. "Plug" up each hole using the plugs/caps you had removed with the apple corer. Simple and fast!
I'd use a different recipe for that part next time. The cream filling was great, so I wound up using a double batch of filling for one batch of cupcakes. I didn't like the idea of pushing it in from the bottom (sounded way too messy for me). So I used a knife and cut a cone shape out of the top, spooned the filling in, and replaced the top. (Just be sure to wait until the cupcakes have cooled, or the cream filling just melts!) Then I frosted them using the great chocolate frosting recipe mentioned, and you can't tell they're anything but chocolate cupcakes until you bite into them.
All you need is a pastry bag and tip. Each cupcake takes about 10 seconds to fill. I made my cupcakes in the pan without wrappers, filled them after they were cool, then arranged a dozen or so to a platter and drizzled them with chocolate ganache. They looked surprisingly elegant for cupcakes. Everyone loved them and ate seconds and thirds. I can't wait to try the same cupcake recipe with different fillings. UPDATE: I have made these cupcakes dozens of times since my first review because they are always requested. I like to ice them with Satiny Chocolate Glaze. I have also filled them with chocolate cream cheese frosting, nutella, and whipped peanut butter frosting. I like to fill them from the top and then spoon the glaze on. After the glaze is set, I pipe a small flower in the center of each cupcake with whatever filling I used.