1 2/3 cups all-purpose flour
1/2 teaspoon baking soda
1/2 cup cocoa
1 1/3 cups sugar
1 1/2 sticks soft unsalted butter
1 tablespoon good-quality vanilla extract
1/3 cup sour cream
1/2 cup water
1 cup semisweet chocolate chips or morsels
Dark chocolate bars for garnishing
1. Let the ingredients sit out so they come to room temperature.
2. Set a baking sheet in the middle rack of your oven; then preheat to 325°. Put the water in a sauce pan on high and bring to a boil. Grease a casserole dish with shortening and set aside.
3. Put the first eight ingredients (everything except the water and chocolate) into a food processor and mix until very smooth. Turn off, and then use a spatula to scrap the mixture off the sides. Pour the boiling water carefully into the food processor, then cover and mix again. Turn off food processor, and then gently mix in the chocolate. Pour batter into the casserole dish.
4. Bake approximately one hour, until a toothpick inserted in the middle comes out clean. Remove from oven, and let it cool on a cooling rack.
5. When cool, cover generously with chocolate frosting (dark chocolate, if available). Grate dark chocolate over the top of the cake for garnish.