Chocolate Chip Coffee Cake

For cake

Position rack in center of oven and preheat to 350F. Butter and flour 10-inch-diameter tube pan, then spray with nonstick spray. Mix egg whites, brown sugar, and salt in bowl. Mix in walnuts and 1/4 cup chocolate chips.

Whisk flour, salt, baking powder, and baking soda in medium bowl.

Using electric mixer, beat sugar and butter in large bowl to blend. Beat in eggs 1 at a time.

Stir in flour mixture in 4 additions alternately with sour cream in 3 additions, beginning and ending with flour mixture. Stir in 1 cup chocolate chips.

Transfer batter to pan smooth top.

Spoon walnut mixture evenly over. Bake cake until tester inserted near center comes out clean, about 1 hour. Cool in pan on rack 10 minutes. Turn cake out onto rack invert onto second rack (walnuts should be on top). Cool. (Can be made 1 day ahead. Wrap in plastic.)

For topping Mix powdered sugar and sour cream in bowl drizzle over cake.