Start by grounding the pistacchios.
Mix the pistacchios with the rest of the dry ingredients: flour, baking powder, and vanilla sugar.
Beat the eggs and add the sugar and the vegetable oil.
Melt the butter and add to the rest of the liquid ingredients.
Gradually add the dry ingredients to the wet ingredients until just combined.
Bake in a pre-heated oven at 375F for about 25min (baking times may vary).
When done, let the cupcakes cook down completely before putting buttercream on top, or put them in the fridge for about 10-15 min. Finish off by putting some pistacchio on top of the buttercream.