Preheat your oven to 350°F (175°C) and line a muffin tray with 12 cupcake liners.

In a large bowl, whisk together flour, black cocoa powder, baking soda, and salt. Set aside.

In a large jug, whisk together eggs, oil, buttermilk, vanilla, vinegar, and sugar until smooth.

Pour the wet mixture into the flour mixture and stir until just combined. Avoid overmixing.

Fill cupcake liners halfway and bake for 18-20 minutes or until a toothpick inserted comes out clean.

Let the cupcakes cool in the tray for 15 minutes, then transfer to a cooling rack. Bake the remaining two cupcakes.

For the frosting, beat butter and confectioners' sugar in a stand mixer until well combined.

Increase speed to medium-high and beat for 2 minutes until thick.

Add salt, vanilla, and cocoa powder to the bowl and beat slowly, then increase speed for another 2 minutes.

Turn the mixer to low speed and pour in heavy cream. Beat until creamy and spreadable.

Use a piping tip to frost the cupcakes.