a piping bag fitted with an open-star tip, such as Wilton 1M; a paintbrush
For the cupcakes: Preheat the oven to 350 degrees F and place cupcake liners in a cupcake pan.
Combine the flour, granulated sugar, baking powder and salt in a large bowl and stir together with a large spoon. Pour in the buttermilk, warm water, oil, vanilla extract and egg vegetable and mix with a whisk until the batter comes together. Fill the cupcake liners about three-quarters of the way full. Bake until a toothpick inserted in the center of a cupcake comes out clean, about 18 minutes.
Allow the cupcakes to cool for 5 minutes in the pan before moving them to a cooling rack to finish cooling. (If you want to accelerate the cooling process, pop the pans into your freezer for about 30 minutes.)
For the vanilla buttercream: Beat the butter in a stand mixer fitted with the paddle attachment on medium speed until smooth, about 30 seconds. Turn the mixer to low speed and slowly add the powdered sugar, 1 cup at a time, alternating with small splashes of cream, until fully mixed. Add the vanilla and salt and beat on low speed until the ingredients are fully incorporated and the desired consistency is reached. (If the frosting is too thick, add additional cream 1 tablespoon at a time. If the frosting is too thin, add more powdered sugar 1/4 cup at a time.)
Place the buttercream in a piping bag fitted with an open-star tip, such as Wilton 1M, and pipe large swirls onto the cupcakes.
Chill the cupcakes in the freezer for 5 minutes to help the frosting firm up.
Use a paintbrush to carefully add tiny bits of gold leaf to the frosting. Garnish with the edible gold dust.