Preheat oven to 350 degrees.

Make sure all your ingredients are room temperature.

In a separate bowl, combine flour, salt, baking powder and soda and mix.

In your mixer fitted with the paddle attachment, blend butter, sugar and vanilla at medium speed until pale and fluffy.

Add eggs, one at a time, scraping the bowl after each addition.

Reduce speed to low and add a cup of flour followed by ⅓ of the buttermilk.

Repeat this 3 times, until you have incorporated all the flour and buttermilk.

Work quickly when you are incorporating the flour and milk.

You do not want to wait until each addition is fully mixed.

I usually add the flour, give it literally 2 seconds, then add the milk, and repeat after 2 seconds. For the last addition of the flour and milk, I usually mix by hand, in order to avoid over beating.

Spoon into greased cupcake pan, and bake for 18-20 minutes.

Cool completely before removing.

Beat butter and extract for 2 minutes.

Add powdered sugar, cocoa powder and coffee.

Beat with whisk attachment for 3 minutes on high.

To assemble, cut one cupcake in half and stick it gently into the bottom of the jar.

Add about 1 tablespoon of filling and place the other half on top.

The filling will spread itself out.

Pipe frosting onto the top, adorn with sprinkles, grab a spoon, and enjoy!