Preheat the oven to 180˚C (350˚F). Cream together the butter and sugar. Add the egg and beat briefly.
Add the vanilla, oil, and food coloring to the butter and mix well.
In a separate bowl, mix together the flour, baking soda, salt and cocoa.
Add the buttermilk and flour mixture in batches until just combined. Do not mix too long.
Divide the batter between 12 cupcake liners and bake in a preheated oven for 18-20 minutes, or until a skewer comes out clean. Allow to cool completely before piping buttercream on top.
BUTTERCREAM WITH WHITE CHOCOLATE
Break the chocolate into pieces and melt in a double boiler. Allow to cool to room temperature.
Mix the butter, confectioners' sugar, and vanilla until creamy and fluffy. This takes about 10 minutes, so a food processor is most convenient. But a mixer will work just as well.
Stir in the cooled and melted white chocolate. Fill a piping bag with the buttercream and pipe it onto the cooled cupcakes in nice swirls. Crumble some red velvet crumbs on top for decoration.