Preheat the oven to 170 ° C. Mix the flour, baking powder and salt together. Mix the melted butter with the brown, white and vanilla sugar. Beat the egg, egg yolk and custard powder until creamy and add to the butter and sugar mixture. Finally stir in the flour mixture. Incorporate chocolate chips.
Spread small piles of dough on a baking sheet lined with baking paper (the piles come apart, so leave 4-5 cm between them) and bake for 10–12 minutes. Let cool down and enjoy with a glass of milk, if possible.