I think you could use store-bought chocolate syrup in this recipe, but the syrup made in the original recipe is not as thick, so store-bought might change the outcome of the cake.
Place the ingredients for the chocolate syrup in a saucepan on the stove and cook over medium high until it reaches a syrupy consistency. Pour into a chilled bowl and place in fridge to cool quickly.
Preheat oven to 350 degrees. Grease and flour a tube pan with removable bottom. Mine has a fairly large center hole of about 4 inches.
Cream butter and sugar. Add eggs, one at a time, beating after each.
Sift together flour, baking powder and salt. Pour milk into the measuring cup and add vanilla.
Add the dry ingredients and the milk to the cake a little at a time, alternating between the two.
Stir the baking soda into the chocolate syrup.
Pour 2/3 of the batter into the prepared tube pan, smoothing out the top.
Mix the syrup into the remaining batter and spread this batter on top of the other batter, again smoothing the top.
Bake for 45 minutes. Then place aluminum foil over the pan and bake an additional 20-25 more minutes or until done.
We usually serve this cake without frosting, but for birthdays, I would add my Italian Chocolate Frosting.
When sliced, the chocolate should have moved down to form a circle in the middle of the cake that the kids say looks like a person's head and shoulders. They get a kick out of the slightly different shape each time the cake is baked.