Cake:
1 1/2 cups unbleached white flour
1/3 cup unsweetened cocoa powder
1 tsp baking soda
1/2 tsp salt
1 cup sugar
1/2 cup vegetable oil
1 cup cold water or brewed coffee
2 tsp pure vanilla extract
2 Tbl vinegar
glaze:
1/2 lb bittersweet chocolate
3/4 cup hot water, milk or half-and-half
1/2 tsp pure vanilla extract
Preheat oven to 375.
Sift together flour, cocoa, baking soda, salt and sugar into an ungreased 8-inch square or 9-inch round baking pan. In a 2-cup measuring cup, measure and mix together the oil, water and vanilla. Pour the liquid ingredients into the baking pan and mix the batter with a fork or small whisk. When the batter is smooth, add the vinegar and stir quickly. There will be pale swirls in the batter where the baking soda and vinegar are reacting. Stir just until the vinegar is evenly distributed throughout the batter. Bake 25 – 30 minutes. Set cake aside to cool, and if you choose to make the glaze, reset the oven to 300.
For the glaze, melt the chocolate in a small ovenproof bowl or heavy skillet in the oven for about 15 minutes. Remove. Stir the hot liquid and vanilla into the chocolate until smooth. Spoon the glaze over the cooled cake. Refrigerate the glazed cake for at least 30 min.