Preheat oven to 325°. Beat butter at medium speed with a heavy-duty electric stand mixer until creamy. Gradually add 1 1/3 cups granulated sugar and 2/3 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.
Bake at 325° 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 1/4 tsp. vanilla at medium-high speed until soft peaks form. Dollop whipped cream onto cake, and sprinkle with shaved chocolate.