Preparation Preheat oven to 350°F. Butter and flour 13x9x2-inch metal baking pan. Bring 1/2 cup sugar, 6 tablespoons butter, and milk to boil in saucepan, whisking until sugar dissolves. Remove from heat. Add chips; whisk until frosting is smooth. Beat remaining 1 cup sugar and 1/2 cup butter in large bowl to blend. Beat in eggs 1 at a time, then chocolate syrup and vanilla. Sift flour, cocoa, baking powder, and salt over; beat to blend. Mix in pecans. Spread batter in prepared pan. Bake until tester inserted into center comes out with moist crumbs attached, about 45 minutes. Cool cake in pan. Spread frosting over cake. (Cake can be made 1 day ahead. Cover and store at room temperature.)
Preparation Preheat oven to 350°F. Butter and flour 13x9x2-inch metal baking pan. Bring 1/2 cup sugar, 6 tablespoons butter, and milk to boil in saucepan, whisking until sugar dissolves. Remove from heat. Add chips; whisk until frosting is smooth. Beat remaining 1 cup sugar and 1/2 cup butter in large bowl to blend. Beat in eggs 1 at a time, then chocolate syrup and vanilla. Sift flour, cocoa, baking powder, and salt over; beat to blend. Mix in pecans. Spread batter in prepared pan. Bake until tester inserted into center comes out with moist crumbs attached, about 45 minutes. Cool cake in pan. Spread frosting over cake. (Cake can be made 1 day ahead. Cover and store at room temperature.)