Preheat your oven to 350 degrees. Then, grease a 9-inch, deep dish pie dish and set aside.

Then, in a medium bowl, make the crisp topping. Add the oats, flour, dark brown sugar, ground cinnamon, and baking powder to the mixing bowl. Use a fork to mix all of the dry ingredients until well combined. Then, add the cold butter to the mixture. Cut the butter into the crisp mixture with a pastry cutter until the mixture resembles pea-sized crumbs. Alternatively, you can use two forks or your hands to make these crumbs — just work fast to ensure your hands don't melt the butter. Once done, place your crumbs into the refrigerator until Step 4.

Next, to a large mixing bowl, add half-and-half, cinnamon, cardamom, nutmeg, vanilla, cornstarch, water, and brown sugar. Whisk until combined. Then, add your sliced apples and toss until everything is well combined and the apples are fully coated.

Next, transfer the apples to the prepared pie dish. Then, remove the crisp topping from the refrigerator and sprinkle the crisp evenly over the apple filling.

Bake the crisp at 350 degrees for 55-60 minutes until the apple filling is bubbling.

Once the crisp is done, remove it from the oven and let it cool for at least 40 minutes before serving, as the filling will need to set.