In another bowl, mix together the sugar and egg. Add the melted butter and melted chocolate to the egg/sugar mixture. Add in the vanilla and buttermilk and red food coloring.
3/4 cup sugar, 1 large egg, 2 tablespoons unsalted butter, 2 ounces unsweetened chocolate, 1/2 tablespoon vanilla extract, 1/2 cup buttermilk, 1 tablespoon red food coloring
Gradually add the dry ingredients to the wet mixture, mixing just until combined. Fill the donut pan with the batter, filling each about 2/3rds full. Bake in the preheated oven for 12-15 minutes.
Icing
In small bowl, stir together all ingredients until sugar is completely dissolved. Use immediately to glaze donuts. You can either toss them in or dip just the tops. If the glaze starts to harden you can add more hot water.