These custard tarts are baked in hearts and require a special heart-shaped mold. In Denmark and Norway, the pastry is known as linser and in Sweden, Vaniljhajrtan. This recipe is from The Nordic Baking Book by Magnus Nilsson.

For the dough:
1 3/4 sticks butter, room temp
1 cup plus 2 tablespoons confectioners' sugar
2 3/4 cups flour
1/2 teaspoon salt
1 egg

For the custard:
1 cup milk
1 cup cream
1 vanilla bean, split in half and seeds scraped out
6 egg yolks
1/3 cup plus 1 1/2 tablespoons sugar
ice, to cool 

Place the butter and the dry ingredients for the dough in a food processor and process until it starts to combine. Add the egg and process until combined. Wrap the dough in plastic wrap and leave it to rest in the refrigerator for at least 30 minutes. 

Meanwhile, make the vanilla custard (see below).

Butter 12 heart-shaped molds and flour them lightly. Place them on a work counter a few centimeters apart. Unwrap and roll out two thirds of the dough to a 1/8 inch thickness. Carefully lift the dough over the molds. Push the dough gently into molds using a clean cloth or something similar, then roll on top of the molds with the rolling pin so that the dough loosens from the edges.

Spoon the cooled vanilla custard into a piping bag and fill the dough-lined molds.

Preheat oven to 345 degrees.

Roll out the rest of the dough on the work counter and place it over the molds as a lid. Press around the edges so that they close completely. Place the molds on a baking sheet and bake for 15 minutes.

Carefully remove the custard hearts from the molds while they are still warm and leave them to cool. Sift some confectioners' sugar on top before serving.  

Vanilla Custard

Pour milk and cream into a pot and place over a medium heat with the vanilla bean and scraped out seeds and bring to a simmer.

Meanwhile, whisk egg yolks and sugar together in a bowl until pale and fluffy. Remove the milk from the heat and add one quarter of the warm milk to the eggs and sugar mix while beating vigorously.

Pour the egg mixture (now containing a quarter of the total milk) back into the pot containing the rest of the milk, while stirring. Return to a low heat, stirring constantly with a large spoon. You can see when the vanilla sauce is beginning to be ready as it will start to thicken. When you are satisfied with the texture, immediately pour the hot mixture into a clean bowl set over ice to stop the cooking and stir until the vanilla sauce is completely cooled down. Strain and serve.