Preheat oven to 375F. Place tart shells on a baking sheet and bake for 10-12 minutes or until they turn a light golden brown.
Carefully remove from their moulds and set aside to cool. Increase oven temperature to 425F.
For the Cheese Filling:
Add all your cheese, butter and milk in a large bowl set atop a saucepan with simmering water (don’t allow the water to touch the bowl). Stir until the cheese and the butter are completely melted and no big chunks of cheese remain (little lumps are ok).
Add confectioner's sugar and cornstarch and stir until well combined.
Then add eggs, lemon juice and vanilla extract.
Continue stirring until the mixture is thick and creamy (see note).
Strain the mixture into another bowl and allow to cool slightly.
For the Egg Wash:
In a small bowl, lightly beat egg yolk with milk and set aside until ready to assemble.
Transfer your custard into your cooled crusts and fill to the brim.
Spoon egg wash over each one (see note) and bake for 10 minutes or until set.
Optional: to get those nice burnt marks on top, you can either use a blow torch or broil the tarts on low for 2 minutes.
Take out of the oven and serve warm.
You can add more cornstarch a little at a time to help you reach the consistency you want.
You should also taste the custard and decide if you want to add more sweetness to it. Add more confectioner’s sugar a little a time, to taste.
You'll need to spoon the egg wash over the tarts because a pastry brush will stick to the surface of the tarts.
See the post for more baking tips, FAQs and step-by-step photos.