Instant coffee intensifies the chocolate richness of these cupcakes. To repeat the Halloween theme, decorate them with plastic cake toppers, licorice, jelly beans, or candy sprinkles. For thicker frosting, cover and chill for 10 minutes before spreading on the cupcakes. Refrigerate frosted cupcakes overnight; cover lightly with plastic wrap, or store them in an airtight container.
To prepare cupcakes, place the first 4 ingredients in a large bowl; beat with a mixer at medium speed until well blended (about 2 minutes).
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour and next 5 ingredients (through 1/4 teaspoon salt), stirring well with a whisk. Stir flour mixture into sugar mixture alternately with buttermilk, beginning and ending with flour mixture; mix after each addition just until blended.
Place 16 paper muffin cup liners in muffin cups; spoon about 2 1/2 tablespoons batter into each cup. Bake at 350° for 18 minutes or until a wooden pick inserted in center of a cupcake comes out with moist crumbs attached (do not overbake). Remove cupcakes from pans; cool on a wire rack.
To prepare frosting, combine powdered sugar and remaining ingredients in a medium bowl. Beat with a mixer at medium speed until combined. Increase speed to medium-high, and beat until smooth. Spread about 1 tablespoon frosting on top of each cupcake.
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