1¾ cups flour
1½ tsp baking powder
1 cup butter
1 cup sugar
1 tsp vanilla extract
1 cup sour cream
zest of ½ an orange, finely minced
¼ cup cocoa
2 tbsp milk
3 ounces Grand Marnier liqueur or other orange liqueur
For the truffle glaze
1 cup dark chocolate chips (I used bittersweet)
1 tbsp butter
3 tbsp whipping cream
Preheat oven to 350 degrees F. Grease and flour a 9 inch spring form pan .
Sift together the flour and baking powder and set aside.Cream together the butter and sugar well. Beat in the eggs, one at a time, beating well after each addition. Beat in the vanilla and sour cream.
Fold in the dry ingredients and divide the batter in half. To one half fold in the orange zest and to the other half fold in the cocoa and milk.
Drop the batter by large spoonfuls randomly into the prepared pan, alternating between the chocolate and orange batters. Swirl slightly with the handle of a wooden spoon if you like for a more marbled effect.
Bake for 40-45 minutes or until a wooden toothpick inserted in the center comes out clean.
Let the cake rest in the pan for about 15 minutes before poking the entire surface of the cake with a wooden skewer. Pour or brush on the Grand Mariner liqueur.
Remove cake, right side up to a wire rack to cool completely.When cool, top with truffle glaze.
For the truffle glaze melt together the chocolate chips, butter and whipping cream in a double boiler.
When melted you can whisk in a small splash of Grand Marnier if you like. Spread over cooled cake.