Preheat oven to 350 degrees F. Grease and flour a 12-cup bundt cake pan, leaving 2 inches at the top for the cake to rise.
In a large bowl, cream butter and sugar together until fluffy. Add eggs, one at a time; beat until fully incorporated.
In a heavy saucepan over low heat, melt chocolate bar or chocolate chips; stirring until smooth. Remove from heat. Learn different techniques for How To Melt Chocolate.
To the melted chocolate, add chocolate syrup and butter-sugar mixture; stir until well mixed.
Add 1/2 the milk mixture to chocolate mixture. Add 1 1/2 cups flour, mixing well. Add remaining milk mixture and remaining 1 1/2 cups flour; beat until well incorporated. Pour into prepared bundt pan.
Remove from oven and cool 15 minutes on a wire rack; remove from pan and invert onto a cake plate. If desired, sprinkle with sifted powdered (confectioner's) sugar over the top of the cake.
Makes 16 servings.
* Learn how to make a Buttermilk Substitution.
Uncle Jimmy's Chocolate Pound Cake Recipe: https://whatscookingamerica.net/cake/chocpoundcake.htm