Preheat the oven to 170°C. Spray a mini muffin tin with low calorie cooking spray.
Unroll the puff pastry. Using a cutter which is slightly larger than each muffin dip, cut 12 circles.
Place each pastry circle into the mini muffin tin, pushing carefully into the sides.
Mix the egg, egg yolk, milk and sweetener in a jug - make sure you whisk until it is fully combined so there is no separation in the egg. Pour into each pastry case.
Sprinkle each custard tart with a little ground nutmeg and bake in the oven for 20 minutes until the pastry is golden and the egg is just set.
Remove from the oven, take out of the tin and leave to cool on a wire rack. Eat as a snack or as part of a dessert!