Preheat oven to 350 degrees. Spray with cooking spray or grease with butter and set aside. line in the cupcake liner into the cupcake pan

In the bowl of a stand mixer, combine butter and sugar and mix on medium speed until very light and fluffy, about 5 minutes. Add the eggs, one at a time, beating well after each addition.

Heat up a pot with water and pour the chocolate in a small bowl and place it over the hot water pot and stir till it's melted, add chocolate, cocoa powder and vanilla extract together; add to the butter/sugar mixture and mix well. Add the salt into the buttermilk.

Add to the batter in three batches, alternating with the flour, In a small bowl, stir together the vinegar and baking soda; add to the batter and mix well.

Fill cupcake line with 3tbsp batter and bake in preheated oven for 17-18 minutes or until a toothpick inserted in the center comes out clean. Do not over bake. Repeat with remaining cupcakes.