The butter must be at room temperature. Whisk the butter and icing sugar till its fluffy. Add the vanilla extract as well and whisk again.
Sieve the cornflour ,custard powder and flour together into the butter mixture. Add the blackcurrants into it. Fold this to forms dough.
Roll it and using a cookie cutter, cut them into desired shapes. Chill the trays with raw cookies, in the fridge for 1 hour.
Bake them at 170℃ , in a preheated oven for 11-14 minutes or till the sides are little brown.
P.S : chill the dough before rolling if it's too sticky to handle. Chilling makes it easy to roll and cut.
