Defrost the dough sheets side by side. Bring milk to the boil, stir 2 egg yolks, sugar and vanilla sugar until creamy, stir in starch. Pour milk into the egg yolk mixture. Pour into the pot, stir and let it thicken for about 3 minutes at medium heat. Pour into a bowl and let it cool down a bit.
Roll out puff pastry sheets rectangularly (each 10 x 20cm) and cut them in half crosswise. Spread with vanilla cream, leaving a margin (approx. 1/2 cm) all around.
Whisk 1 egg yolk with 2 tablespoons of water. Place 1 apricot in each of 2 opposite corners of the dough squares, beat free corners over it and brush with egg yolk mixture. Bake in the preheated oven (electric cooker: 200°C/circulating air: 175°C/gas: see manufacturer) for approx. 20 minutes. Let them cool down.