In a large bowl, whisk together the egg yolks and whole egg.
Add the sugar, and whisk again.
Sift in the flour, add the vanilla pod and pour in the milk.
Whisk well to avoid lumps from forming.
Transfer the mixture to a sauce pan and simmer on a low heat until it thickens.
Remove from the heat and leave it to cool completely.
Preheat the oven to 200 degrees Celsius (390 Fahrenheit, 160 fan oven).
Transfer the puff pastry roll to a working surface and use a cookie cutter to cut 12 rounds that fit in the muffin tin holes.
Press the rounds into the muffin tin holes and spoon in the custard cream evenly.
Bake for 30-35 minutes or until golden and the pastry is baked through and the custard is golden, and slightly brown.
Allow them to cool, then use a sharp knife to ease up the edges and transfer the tarts to a plate.
Once out of the oven, the custard will sink in, so not to worry if in the oven the tarts looked popped out.