Hong Kong Style Egg Tarts

* 4 medium eggs, beaten (reserve 2 tablespoons for your pastry dough)

* 3/4 cup hot water

* 6 Tbsp. sugar

* 1/8 teaspoon salt (pinch of salt)

* 1/4 cup evaporated milk

* Dash of vanilla (optional)

* 2 cups cake flour, plus extra for dusting

* 1 stick unsalted butter, room temperature

* 1/4 cup powdered sugar

* 2 tablespoons of beaten egg

* 1/8 teaspoon salt

* Dash of vanilla (optional)