Serves: 48 mini cupcakes
Preheat the oven to 170#~°C. Line 48 mini muffin cups (2 large tins or 4 small) with paper liners.
Whisk together the flour, cocoa and 1/4 teaspoon of the salt in a medium bowl. Beat together the oil and granulated sugar on medium-high speed with a hand mixer in a large bowl until well combined. Add the egg and beat until well blended. Beat in the food colouring and 1/2 teaspoon of the vanilla.
On low speed, alternately add the flour mixture and buttermilk in thirds, beginning and ending with the flour, beating well after each addition. Whisk together the baking soda and vinegar in a small bowl, and then beat into the batter until fully incorporated.
Using a small ice cream scoop sprayed with nonstick cooking spray, evenly divide the batter among the cupcake liners. Bake until a toothpick inserted in the center of a cupcake comes out clean, 18 to 20 minutes. Remove the cupcakes from the tins and cool completely on a wire rack.
Meanwhile, beat the cream cheese in a large bowl until smooth and fluffy. Sift the confectioners' sugar over the mixture and beat until smooth. Beat in the remaining 1/4 teaspoon salt and 1/2 teaspoon vanilla. Spread or pipe the frosting over the cooled cupcakes.