FOR CHOCOLATE GANACHE FROSTING (Makes about 1 & 2/3 cup and the extra can be used for fudge sauce over ice-cream because it will keep in the fridge for up to two weeks):.
In a medium sauce pan, heat the cream and the butter over low heat until the butter has melted, but do not let simmer or boil.
Remove pan from heat and stir in the chocolate chips.
Let the chocolate chips sit in the hot cream to soften.
Stir in the vanilla extract until the chocolate has melted.
FOR MOCHA MOUSSE FILLING:.
In a large bowl, beat the whipping cream, sugar, and instant coffee with a hand mixer until the the coffee dissolves, and then up the speed to medium-high and beat until stiff peaks form.
Fold the 3/4 cup chocolate ganache filling into the whipping cream mixture a little at a time .
Chill the mousse filling in the refrigerator for at least 30 minutes, as it needs to be really cold when you fill the cooled cupcake bottoms (otherwise the filling will run).
Melt chocolate over simmering water in a double-boiler or heat proof bowl. Once melted and smooth, let it cool slightly.
Sift flour, baking powder, salt & soda into a bowl.
In a large bowl or stand mixer, beat butter and sugar together until creamy (about 2 minute with stand mixer on high).
On low speed, add in the melted chocolate until combined.
On medium speed add the eggs one at a time until smooth.
Add in the vanilla and beat until the mixture is creamy (color should be slightly lighter).
Mix in the sour cream until no white streaks remain, but don't over mix.
On low speed, add half of the flour mixture until it is incorporated-don't over mix.
Add in the water and mix it until incorporated.
Scrape bowl and add in the rest of the flour and mix on low until flour is incorporated and batter looks pretty smooth (again, don't mix too much or the cupcakes lose lightness).
Preheat oven to 350 degrees and put rack in the center of oven.
Fill each liner up to the top of liner.
Bake 22-24 minutes.
Cupcake tops should feel firm and a toothpick inserted in the center should come out clean.
Cool the cupcakes for 10 minutes in the pan on a wire rack.
Remove the cupcakes from the pan onto a wire rack and let cool completely.
Once cupcakes are fully cooled, use a sharp knife to slice the top off each cupcake (this is so you can fill them).
Place cupcake tops right side up on a wire rack, and set aside cupcake bottoms on a serving platter.
To frost cupcake tops, spread one tablespoons of the chocolate ganache frosting over the top of each cupcake top.
Let cupcake tops cool until the ganache frosting is firm.
Next, place a dollop of mocha mousse filling on each cupcake bottom. Using a wide metal spatula, carefully place the cupcake tops w/ cooled frosted ganache topping on top of the mousse filled cupcake bottoms.
It may help to refrigerate the assembled cupcakes for about 30 minutes to an hour before serving so that everything firms up.