In a small bowl, combine the buttermilk, oil, eggs and vanilla. Pour the buttermilk mixture into the dry ingredients and beat just until smooth. Add coffee and mix just until incorporated. Divide the batter evenly into the prepared pans. Bake for 35 to 40 minutes, or until a toothpick inserted in the center comes out clean. Cool the cakes in the pans for 10 to 15 minutes, then run a knife around the edges, turn the cakes out onto a wire rack and peel off the parchment paper.
To make the frosting, place the marshmallows on a cookie sheet lined with parchment paper. Place on lower rack of oven, and broil marshmallows until nice and brown on top, between 30 to 60 seconds. Remove pan from oven and gently turn the marshmallows over, and broil until they are golden brown. (Be sure to keep an eye on them because they burn very quickly.)
*Nutritional information is an estimate. Please consult a doctor or nutritionist for the most accurate nutritional info.