Begin by melting 3 tablespoons of butter in a large skillet over medium heat. Add 2.5 pounds of peeled, cored, and diced gala apples along with ½ tablespoon of apple pie spice. Stir and cook for about 5-7 minutes until the apples soften. Remove from heat and set aside to cool slightly.

In a large mixing bowl, cream together 6 tablespoons of softened unsalted butter with ½ cup of brown sugar and ¼ cup of white granulated sugar until light and fluffy. Beat in 1 room temperature egg and 1 teaspoon of vanilla extract until well combined. Gradually mix in 1 cup plus 2 tablespoons of all-purpose flour, ½ tablespoon of apple pie spice, ½ teaspoon of baking soda, and a pinch of salt until just combined.

Preheat your oven to 350°F (175°C). Grease a 9-inch pie dish and press the cookie dough evenly into the bottom and up the sides. Bake in the preheated oven for 10 minutes, or until the crust is lightly golden at the edges. Remove from the oven and let cool slightly before assembling the pie.

Spread half of the dulce de leche over the pre-baked cookie crust, allowing it to seep slightly into the warm crust. Spoon the cooked apple filling over the dulce de leche, distributing the apples evenly.

Combine ½ cup of brown sugar, ¼ cup of white granulated sugar, 1 teaspoon of apple pie spice, and ¾ cup of flour in a medium bowl. Pour in 4½ tablespoons of melted butter and mix until the streusel resembles coarse crumbs. Sprinkle generously over the apple filling.

Return the pie to the oven and bake at 350°F (175°C) for 25-30 minutes, until bubbling slightly around the edges and the topping turns golden brown. Watch to prevent over-browning.

Drizzle any remaining dulce de leche over the warm pie. Allow cooling for at least 15-20 minutes before slicing. Serve with cream or ice cream if desired.