Chocolate-Swirled Pound Cake

Beat the butter on medium speed with an electric mixer for 2 minutes or until creamy. Gradually add the sugar, whisking for 5-7 minutes. Add the eggs, 1 at a time, beating until the yellowness disappears.Add the flour to the butter mixture alternately with the milk, starting and ending with the flour. After each addition, beat on low speed until smooth. Add vanilla.Combine 1 cup of the batter and the chocolate syrup, stirring occasionally, until smooth.Divide the remaining dough in half; pour 1 serving into a greased and floured 10-inch-diameter pan. Place half of the chocolate batter on top; repeat layers. Gently beat the dough with a knife.Bake at 300 ° C for 1 hour and 40 minutes, or until a wooden stick inserted in the middle comes out clean. Cool in the pan on a wire rack for 10 minutes; remove from the pan and allow to cool completely on the wire rack.