Beat the butter until thick and creamy, add the egg yolks and vanilla sugar, beat until very thick and creamy, stir in the liqueur well.
Fill the amount with a piping bag into the hollow capsules, fill the semi-sweet cooking chocolate warmed in a water bath into a paper piping bag and decorate the pralines with it, finally a touch of ground hazelnuts.
Tip: Do you prefer milk chocolate or dark chocolate? Depending on the case, use whichever you like better.