The original Black & Tan is a layered drink of pale ale and dark beer served in British pubs. My Black & Tan looks like the drink but veers off in a sweet direction, alternating chunks of chocolate cake and scoops of ice cream in a Pilsner glass and topping it with whipped cream, to resemble beer foam.
If you don't have time to start from scratch, you can use store-bought chocolate cake and ice cream, and your guests will still sit up and take notice when they see this dessert coming to the table.
For the cake: Preheat the oven to 325 degrees F and position a rack in the middle. Butter an 8-inch square baking pan.
Pour the batter into the baking pan and smooth the top. Bake for 35 to 40 minutes, until a toothpick inserted in the center comes out clean. Cool completely on a rack.
To assemble the black & tans: Invert the cooled cake onto a work surface and cut it into 6 equal rectangles. Cut each rectangle into squares about the size of ice cubes. Set out six Pilsner or similar glasses. Put 2 rounded scoops of ice cream into each glass. Divide the cake cubes evenly among the glasses, then add 1/2 scoop of ice cream to each glass, mounding it slightly in the center. Top with softly whipped cream to look like the frothy head on a pint of stout, allowing a drip to edge over the side. Serve immediately.
Chocolate Cake Batter
Sift the flour, cocoa powder, baking soda, and salt onto a piece of waxed paper or into a medium bowl.
With an electric mixer on medium speed, beat the butter and the sugar until light and fluffy, about 3 minutes. Add the oil, beating well. Beat in the egg, then the vanilla. On low speed, add the dry ingredients in 3 batches, alternating with the buttermilk, beginning and ending with the dry ingredients, scraping down the sides of the bowl and mixing just until the batter is smooth.