Preheat oven to 350 degrees. Spray a 12-cup muffin tin with non-stick cooking spray.
In a mixer fitted with a paddle attachment, add the butter, 1 cup brown sugar, and 1/2 cup granulated sugar. Beat everything until nice and fluffy. Next, add in the eggs and vanilla. Continue to combine.
Add in the flour, oats, baking powder, cinnamon, and kosher salt. Stir to combine.
Using an ice cream scoop, scoop the cookie dough into the muffin tin and using your hands press to flatten. Bake the cookie cups until golden brown; about 15 to 20 minutes.
Remove the cookies from the oven. Spray the bottom of a shot glass with cooking spray and gentle press the shot glass into the center of each cookie to create cups. Let the cookie cup cool in the muffin tin before removing.
Next, melt 2 tbsp butter in a skillet over medium-high heat. Add the apples and cook until beginning to soften. Add 1/4 cup brown sugar, 1/4 cup granulated sugar, cornstarch, nutmeg, and cinnamon. Cook until softened and caramelized.
Remove the cookie cups from the muffin tin and place on a serving tray. Spoon the apple filling into each cup. Garnish with caramel and whipped cream!