1. Whisk egg yolks, sugar and cornstarch until smooth and slowly pour your warm milk; transfer to the stove over medium low heat and start stirring until it thickens; optionally, run it through a sieve for extra smoothness, stir in vanilla bean paste and transfer into a pastry bag and refrigerate until cool;
2. Roll your puff pastry dough over a floured surface and cut it into 12 strips; roll each strip onto a metal horn as you make sure it overlaps half way of its width; brush egg wash and sprinkle coarse sugar and/or crushed pistachios;
3. Bake at 400 F for about 20-22 mins;
4. Transfer the horns on a cooling rack and fill them in with the cooled custard;
5. Sprinkle some powdered sugar, serve with with berries, mint leaves and the remaining custard for extra dipping and enjoy!
