Black Forest Pound Cake

2/3 c butter, softened
1 1/3 cup granulated sugar
2/3 c firmly packed dark brown sugar
4 large eggs
1 ¼ teaspoons vanilla extract, divided
1 1/2 cups cake flour
1/2 c unsweetened cocoa
1/2 tsp. salt
1/4 tsp. baking soda
3/4 c sour cream
3 (1 oz.) bittersweet chocolate baking squares, finely chopped
Whipped Topping:
1 1/4 cups heavy cream
1 tbsp. granulated sugar
Shaved bittersweet chocolate
Cherry Sauce:
2 (12-oz.) packages frozen cherries
1/3 c sugar
1/3 c cold water
2 tsp. cornstarch
2 tbsp. Kirsch or brandy
1/2 tsp. vanilla extract
Pinch of salt

Preheat oven to 325 degrees. Beat butter at medium speed with a heavy-duty electric stand mixer until creamy. Gradually add 1 1/3 cups granulated sugar and ⅔ cup brown sugar, beating until light and fluffy (about 5 minutes). Add eggs, 1 at a time, beating just until blended after each addition. Beat in 1 tsp. Vanilla.
Whisk together flour and next 3 ingredients. Add to butter mixture alternately with sour cream, beginning and ending with flour mixture. Beat at low speed just until blended after each addition. Stir in chopped chocolate.
Pour batter into a greased 10-inch round cake pan (with sides that are 3 inches high).
Bake at 325 degrees for 1 hour and 10 minutes to 1 hour and 20 minutes or until a wooden pick inserted in center comes out clean. Cool in pan on a wire rack 15 minutes. Remove from pan to wire rack; cool completely (about 1 hour.)
Meanwhile, prepare Cherry Sauce. Place cake on a serving plate or cake stand. Slowly pour Cherry Sauce over cake. Beat heavy cream, 1 Tbsp. granulated sugar, and remaining ¼ tsp. Vanilla at medium-high speed until soft peaks form. Dollop whipped cream onto cake, and sprinkle with shaved chocolate.
Cherry Sauce:
Stir together cherries, sugar, cold water, and cornstarch in a medium saucepan. Cook over medium-low heat, stirring often, 12 to 15 minutes or until thickened. Remove from heat, and stir in Kirsch or brandy, vanilla, and salt. Cool completely (about 1 hour).