Preheat oven to 175C.
Spray the tops of 30-32 hole muffin trays.
Line trays with large patty papers. Set aside.
In a medium sized bowl, sift together the flour, cocoa and salt. Use a wire hand whisk to whisk the cocoa through. Set aside.
Using an electric mixer, beat the butter for approximately 2 minutes until soft and creamy.
Add half the sugar and beat on medium speed until it starts to change colour.
Add the rest of the sugar and the vanilla and beat until combined. Scrape the sides and bottom to ensure all the butter gets mixed into the sugar.
Increase speed to medium-high and beat until for approximately 3 minutes until light and fluffy, scraping the sides of the bowl at least once.
Add eggs, one at a time, beating well after each addition. Scrape sides of the bowl.
Carefully mix in the red food colouring, then mix well.
With the mixer on low speed, start adding the flour and buttermilk alternately, in three or four lots, beginning and ending with the flour. Scrape down the bowl sides each time to ensure the red and the cocoa combine properly.
Increase speed and mix until the colour is even.
Place bicarbonate of soda in a cup or 250 mL jug.
Add the vinegar and mix quickly and then fold well into the batter.
Using a lever-action ice-cream scoop, drop 1 full scoop into each patty paper.
Bake on middle shelf of oven for 22-24 minutes. Cool in the tins for 5 minutes then tip out onto wire racks to cool.
Peanut butter buttercream : Whip the butter for 2-3 minutes on high speed.
Add the icing sugar, milk and vanilla.
On low speed, mix the sugar into the butter until combined.
Increase the speed to high and beat for at least 5 minutes or until the cream is almost white.
Add the peanut butter and beat until mixed through.
Pipe onto cupcakes using a large rosette tube. Sprinkle with crushed nuts and chocolate sprinkles.
