Preheat the oven to 180°C (350°F) and line two cupcake trays with cupcake papers.
Add the oil, eggs, and sugar to a bowl of a stand mixer fitted with a whisk attachment. Beat on medium-high speed until combined, about 2 minutes.
Sift together the salt, baking powder, cocoa powder, and flour. Add the flour mixture to the egg and sugar mixture. Beat at low speed until just combined.
In a large jug combine the buttermilk and vanilla. Slowly pour this into the cupcake batter with the mixer's motor running at low speed. Scrape down the sides of the bowl and mix again, making sure it is lump-free.
Add about ½ a teaspoon of black gel food coloring to the cupcake batter and beat again until well combined and dark in color.
In a small bowl combine the baking soda and white vinegar, add this to the cupcake batter and fold this through with a rubber spatula.
Divide the batter between the 24 cupcake liners, filling them ⅔ of the way up the liner. Bake in a preheated oven for 12 – 15 minutes or until a toothpick inserted into the center comes out clean. Cool completely on a wire rack.
Black Frosting
In a bowl of an electric mixer fitted with a paddle attachment, add the butter, cocoa powder, and icing sugar. Beat at medium speed until the mixture looks like fine breadcrumbs.
In a jug combine the cream and vanilla, with the mixer's motor running at low speed slowly add the cream mixture. Continue until it has all been added. Then increase the speed of the mixer to medium-high. Beat until light and fluffy, scraping down the sides of the bowl often.
Add about ½ a teaspoon of black gel food coloring to the frosting and beat again until well combined and dark in color.
Fill a prepared piping bag with the frosting and pipe a swirl onto each cupcake. Decorate the top of each cupcake with edible homemade or store-bought pumpkins. Enjoy!