Begin by preheating the oven to a temperature of 350 degrees Fahrenheit.

Prepare a regular muffin tin by applying baking spray or greasing it. Note that you will need to use this twice, or alternatively, prepare two muffin tins.

Proceed to cut out twenty-four circles, each two inches in diameter, from the pie crust dough. Should you have excess dough after the initial cutting, gather the scraps and re-roll them to a thickness of ¼ inch.

Place each of the pie crust circles into the wells of the muffin tins.

In a small saucepan, combine the diced apples, granulated sugar, cinnamon, lemon juice, and cornstarch. Cook this mixture over medium heat for approximately 5 to 7 minutes, or until the apples have softened and the mixture has thickened.

For the crisp topping, take a separate bowl and add the all-purpose flour, ½ cup granulated sugar, light brown sugar, kosher salt, rolled oats, and diced cold butter. Use a hand mixer or pastry cutter to mix these ingredients until the mixture achieves a crumbly texture.

Distribute one tablespoon of the apple filling into each of the pie crust-lined muffin wells.

Following this, add two tablespoons of the crumble topping over each filled muffin well.

Optional: For a more cohesive topping, lightly spray the tops with canola oil. This is not a mandatory step and can be omitted based on preference.

Place the muffin tin in the preheated oven and bake for a duration of 18 to 20 minutes, or until the tops are golden brown.

After baking, remove the muffin tin from the oven and allow the cookies to cool completely. Once cooled, carefully remove the cookies from the tin.