Preheat your oven to 150°C.
Beat the butter with a mixer until fluffy.
Put the flour in a separate bowl. Add the baking powder, icing sugar, hazelnut oil and butter and then mix.
Cover a baking sheet with baking parchment. Make bottle cap-sized balls of the dough using a piping bag or a spoon and place them on the sheet.
Bake them for 8-10 minutes but don't let them brown. Don't open the oven door during baking.
Once baked, let them cool down on the baking sheet.