This recipe can be cut in half, if you want to top your cake with a thinner layer of frosting.
1 cup (2 sticks) margarine (such as Earth Balance®), melted and cooled
1 1/3 cups unsweetened cocoa powder, sifted
4 1/4 cups powdered sugar, sifted
1/4 cup hot strong brewed coffee
2 tablespoons soymilk
1 tablespoon dark rum or soymilk
2 teaspoons pure vanilla extract
In a medium bowl with an electric mixer, beat together the melted margarine, cocoa powder and half of powdered sugar, beating until smooth. Add the rest of the powdered sugar, coffee, soymilk, rum and vanilla, beating frosting until smooth and fluffy. If frosting is too thick, add an additional tablespoon or so of milk. Spread frosting on top of cooled cake and serve.