• Preheat oven to 350 degrees F. Grease 3 8-inch round cake pans. Line with parchment circles (if you want) then grease and flour again.
• Also, prep your piping bags. If using zipper bags, make sure they are the heavy duty ones and snip off the tip at about ½ inch. If using piping bags, fit them with ½ or larger tips.
• Whisk together flour, baking powder and salt; set aside.
• Cream the butter and sugar in bowl of a stand mixer using paddle attachment. Beat in the vanilla.
• Add eggs one at a time, beating well after each addition. Scrape side of bowl often.
• By hand or using lowest speed of mixer, beat in the flour and ¾ cup milk (reserve the 1 T.) alternately, beginning and ending with the flour mixture.
• Divide batter in half. The best way is with a scale. If you have a scale, set a second bowl on it, set tare to zero and weigh out about 17 oz which is about half the batter.
• Stir the melted chocolate into half the batter along with the reserved 1 tablespoon milk.
• Divide batter evenly between 2 decorating bags.
• Pipe the batter into the pans in this order. Start with the chocolate batter and pipe a circle of chocolate around the edge of one pan. Pipe a ring of vanilla inside the chocolate. Pipe a circle of chocolate in the middle. Repeat with the second pan. For the third pan, pipe the vanilla around the edge, add a circle of chocolate and a middle circle of vanilla.
• Bake pans on center and lower racks, staggered, for 20 to 25 minutes or until a toothpick inserted in cakes comes out clean. Let cool in pan set on a rack for 10 minutes. Remove from pans and peel off parchment. Cool completely.

Frosting

• Take the time to sift the powdered sugar and cocoa powder if lumpy.
• In a mixing bowl, using an electric mixer, beat the butter until light and fluffy.
• Add half of the sugar and all of the cocoa powder and stir until it holds together, then beat until creamy.
• Add vanilla, salt and remaining sugar and beat until blended, then gradually (1 tablespoon at a time) add your whole milk or cream mixture, beating and scraping the sides of the bowl until icing is smooth.

Assembling

• To assemble the cake, start with a chocolate-vanilla-chocolate ringed layer. Spread with a thin coat of frosting, then stack on the vanilla-chocolate-vanilla layer. Spread that with frosting, then add the other chocolate-vanilla-chocolate layer. Spread frosting all over the cake