Take 1/4 cup coffee. Dissolve instant coffee until close to solubility limit. Add 1/4 cup buttermilk and 1 cup sugar.
In another bowl, beat 1 stick butter (must be at room temperature, not cold or melted), 2 eggs, and 1 cup sugar. At vanilla and any other desired spices, 1/2 cup buttermilk, 1 tsp baking soda, and 2 cups cake flour (must be sifted).
Comebine all, bake 350 F for ~30 minutes. Cake pans will require a was paper insert on the bottom or there's no way they will ever release.
For frosting, take some coffee, maybe 1/4 cup, and reheat it if it's cold. Put in 3/4 cup cocoa powder. Add more hot coffee if the cocoa doesn't dissolve (solubility of cocoa powder is significantly dependent on liquid temperature). Put in bowl with 3/4 stick butter. Mix and add powdered sugar until consistency is correct for spreading.