Here is the recipe for the famous Pastéis de Nata, you may know them as custard tarts. My father makes the best ones (better than the ones sold on bakeries), but he doesn't follow a recipe so I can't actually put it in paper.
Still with this recipe you'll get the idea of how it's made.
Puff Pastry 600g fresh or purchase
500 ml milk
1 lemon peel
1 cinnamon stick
250 ml water
7 egg yolks
1. With rolling pin, stretch the dough into a rectangle.
Wrap the dough in a roll, pressing well.
Cut dough into slices with thickness of 1.5 cm.
2. Place the slices into the shapes of biscuits, smeared with butter.
With your thumbs, start pushing the center of the dough and spread it until the edges so that they become thicker, making the dough more thin on the bottom.
Place the shapes on a baking tray.
3. Dissolve the flour in a little milk.
Bring the remaining milk to boil, add the cinnamon stick and lemon peel.
When boiling, add the flour and stir well.
Stir until it begins to boil and turn off the heat.
4. In a pan, bring to boil sugar and water and stir.
After starting to boil, let boil for exactly 3 minutes.
Add the sugar syrup in a thin milk and mix well.
Strain in a colander and let it cool
NOTE: Leave it to cool until cold.
5. Add the egg yolks with the cream and stir well.
Fill the shapes with the cream.
Bake in preheated oven at 250 degrees for 17 minutes.
6. Once cooked, unmold.
Serve hot or cold, sprinkled with powdered sugar or cinnamon.
You don't have to sprinkle the cinnamon nor the icing sugar, the custard tart is already sweet and delicious without it. I prefer it without any sprinkling.
Here is a pic of a finished custard tart without any sprinkle of cinnamon or icing sugar.