For cupcakes 6 ounces unsweetened chocolate, chopped 2 cups cake flour 1 teaspoon baking soda 1 cup buttermilk at room temperature 1 teaspoon pure vanilla extract 2 sticks unsalted butter at room temperature 1 cup granulated sugar 1 cup light brown sugar 4 large eggs
Preheat oven to 350 degrees. Line 2 1-dozen cupcake tins with cupcake papers.
Melt the chocolate over a double boiler or in a microwave. Set aside and allow to cool for 15 minutes. In a small bowl, mix the flour and baking soda. In another small bowl, mix the buttermilk and vanilla, and set both bowls aside. Using a hand or stand mixer, cream the butter, granulated sugar and brown sugar together. Add the chocolate and the eggs, one at a time, and mix until incorporated. In three additions, add the flour and buttermilk mixtures alternately until just combined. Divide between the cupcake tins and bake 20 to 25 minutes until a tester comes out clean. Allow to cool completely before icing. To make the icing, use a hand or stand mixer to cream the butter until light and fluffy, about 5 minutes. Over a double boiler or in a microwave, melt the chocolate and allow to cool for 20 minutes. After chocolate has cooled, add it to the creamed butter and mix on low until just combined. Scrape sides of bowl, then add sugar, milk and vanilla, and mix on low until fully incorporated. Mixture should be smooth and medium brown in color. Use immediately or store in airtight container for up to 2 days. Do not refrigerate.