In a food processor, combine 2 cups of all-purpose flour, 1 cup of cold unsalted butter, 1 egg yolk, 3 tablespoons of milk, and a pinch of salt. Pulse until the mixture resembles coarse crumbs, about 15-20 seconds.

Preheat your oven to 350°F (175°C). Grease a 13x9-inch baking pan. Take half of the dough and press it into the bottom of the pan to form an even crust layer.

In a large bowl, combine 4-5 sliced Granny Smith apples with ¾ cup of granulated sugar, 2 tablespoons of flour, 2 teaspoons of vanilla extract, and 1 teaspoon each of cinnamon and nutmeg. Toss gently.

Spread the apple filling evenly over the bottom crust. Crumble the remaining half of the dough over the top of the apples.

Brush with egg wash made from a beaten egg and a tablespoon of water. Sprinkle 2 tablespoons of turbinado sugar over the top. Bake for 35-40 minutes until golden brown.

Let them cool in the pan for at least 30 minutes, cut into bars and serve warm or at room temperature.