Milk Chocolate Bundt Cake

The recipe came from the Taste of Home Baking cookbook
1 milk chocolate candy bar, (7 ounces) (I used semi-sweet because that’s what I had)
1/2 cup chocolate syrup (I used dark chocolate syrup because that’s what I had)
1 cup butter, softened
1-1/2 cups sugar
4 eggs
1 teaspoon vanilla extract
1/2 teaspoon baking soda
1 cup buttermilk
confectioners’ sugar, optional

The chocolate. [...]