01 -
Heat milk until it’s steaming but not bubbling. Beat together yolks, sugar, vanilla, and flour until smooth and airy. Slowly pour in the heated milk while whisking. Put the mixture over medium heat, stirring constantly, until it thickens. Let it cool and chill for at least an hour in the fridge.
02 -
Fire up your oven to 400°F. Flatten the puff pastry and sprinkle with sugar. Stretch it to roughly 9x12 inches. Slice it into 12 strips, each 1 inch wide.
03 -
Wrap each pastry strip around the horn molds, overlapping as you go. Lay them seam-side down on a tray lined with parchment.
04 -
Whisk together the egg and a splash of water. Lightly coat the pastry tops with this mix but avoid touching the molds.
05 -
Pop in the oven for 15-20 minutes until they’re golden brown. Let them cool down a bit before carefully slipping them off the molds.
06 -
Pipe the chilled custard into the cooled pastry horns. Sprinkle a bit of powdered sugar over the top before eating.