That chocolate frosting

The recipe for that chocolate frosting I'm always referring to is actually a recipe for Mocha Buttercream Frosting. It offers a variation for Chocolate Buttercream Frosting, so see below for those changes from the original recipe here:

Mocha Buttercream Frosting:
Makes 2 cups, enough to fill and frost an 8-inch round 2-layer cake

Note from the author, Carol Gelles:
Mocha is a hard flavor to pin down -- not quite chocolate and not quite coffee. I think this frosting has a good balance between the two flavors. If you prefer mocha with a strong coffee flavor, halve the cocoa; for a more chocolatey flavor, use less coffee and 1 tablespoon more cocoa.

Note from Mel:
I always make a 9-inch round 2-layer cake and this much frosting is NOT quite enough, so I would recommend 1.5X or 2X the recipe for that size. . . 2X if you want left-overs for spontaneous cupcakes later in the week (not that I've done that).

1 Tbs. hot water
1 1/2 tsp. instant coffee granules
1/2 cup (1 stick) butter, softened
1/4 cup unsweetened cocoa
3 Tbs. sour cream
3 1/2 cups sifted confectioner's sugar (I usually don't measure this, OR sift. . . I just add it a little at a time and mix it well until the frosting's a good spreading consistency)

1. In a small bowl, stir together the water and coffee until the coffee is disolved.
2. In a large bowl, beat the butter until light and fluffy. Beat in the cocoa until completely combined. Beat in the coffee and sour cream. (Using a stand mixer doesn't mix this well enough. . . so while I DO use mine, I also have to get in there with a metal spoon to make sure it's really mixed well. . . it's annoying, but otherwise you're going to have spots of chocolate throughout later).
3. Beat in the confectioner's sugar one cup at a time until all the sugar has been incorporated.

Variation: Chocolate Buttercream Frosting: Omit the instant coffee and water and use 2 tablespoons milk instead.