These are my take on Portuguese custard tarts – simply irresistible!
Whisk together half the sugar with the 1 yolk, 2 whole eggs, lemon juice, lemon rind and vanilla in a medium bowl.
Whisk the cornstarch, remaining sugar and milk in a bowl or measuring cup. Bring milk to a boil in a saucepan over medium heat. Cook until slightly thickened. Slowly, whisk into egg mixture. Return to sauce pan and bring back to a boil, stirring constantly. Transfer to a bowl. Cover with plastic wrap, sealing plastic wrap directly over the custard so that no skin forms on the custard. Put in refrigerator and thoroughly chill before using, about 1 to 2 hours.
Preheat oven to 400 degrees F.
Roll out the puff pastry to 1/8-inch thick. Cut the pastry into twelve 4-inch circles with a cookie cutter or top of a cup or glass. Press pastry circles into muffin cups. Prick the bottoms with a fork. Line each puff cup with aluminum foil. Fill with pie weights or dried beans. Bake for 12 to 15 minutes. Remove from oven. Remove foil and pie weights. Cool pastry for 5 to 10 minutes.
Preheat oven to 350 degrees F.
Spoon the cooled custard into the baked puff pastry cups. Bake until golden and skin forms, about 10 to 15 minutes. Let tarts cool to room temperature. Serve at room temperature or chilled. The custard will be a little loose.