Preheat oven to 350°F.
Start by melting the butter in a saucepan on the stove. Once the butter is melted, add in the instant coffee. Pour in the boiling water and remove from heat. Whisk until fully combined and then set aside.
In a large bowl, add flour, sugar, salt, and baking soda. Pour butter mixture over and whisk together.
In separate bowl mix buttermilk, eggs, and vanilla. Pour over batter and whisk until fully combined.
Prepare pans. I used two 8in rounds. Pour batter into pans and cook for 16-22 minutes or until an inserted toothpick is removed clean.
Let the cakes cool to room temperature then cut them each in half, creating four layers instead of two. You may need to level the cakes slightly if there is a large dome.
Eat the scraps immediately, and tell no one.
I then placed all the layers in the freezer for two hours.