1. Preheat oven to 350 degrees F. Line a 12-cup muffin pan with paper liners.

2. In a mixing bowl, beat oil, sugar, egg, and vanilla with an electric mixer at medium speed until smooth.

3. In another bowl, sift together flour, cocoa, baking soda, and salt.

4. Add dry ingredients alternately with buttermilk to oil mixture. Beat at lowest speed with an electric mixer, being careful not to overmix. Divide batter evenly among prepared muffin cups.

5. Bake for 20 to 25 minutes, or until a tester inserted near center comes out clean.

6. Cool for 10 minutes in pan. Remove cupcakes from pan and let cool completely on wire racks. Frost cooled cupcakes with Marshmallow-Creme Icing.

7. Garnish with coarse sugar.

8. Marshmallow-Creme Icing: In a mixing bowl, beat all ingredients at medium speed with an electric mixer until light and fluffy.