Sift together the all-purpose flour and kosher salt into a bowl and set aside.
In a stand mixer fitted with the paddle (or using a hand mixer), beat the room-temperature unsalted butter with the granulated and powdered sugars until smooth and creamy.
Whisk the egg yolks with the whole milk and vanilla extract in a small bowl, then gradually add to the creamed butter while mixing, scraping the bowl as needed.
On low speed, add the flour mixture gradually and mix until the dough just comes together; if it seems dry, add additional milk 1/2 teaspoon at a time until cohesive.
Form the dough into a disk, wrap in plastic wrap, and chill in the refrigerator for 1 hour.
Preheat the oven to 350°F (175°C).
Roll the chilled dough on a lightly floured surface and cut into rounds sized for your mini tart pans or muffin tin; press each round into the molds and prick the bottoms with a fork.
Chill the lined tart shells for 15 minutes, then bake for 12–15 minutes until the edges are golden; cool in the pans briefly before removing.
