Peel apples, remove the seeds and cut apples into large chunks, about 1.5 inches.
Place the chunks in a bowl of water and 2 Tablespoons lemon juice to keep the apples from turning brown.
Once all apples are chopped, place the apples into pressure cooker cooking pot.
Mix in 2 Tablespoons lemon juice and sugar over apples and mix through.
Let the apples sit for 10 minutes so that they will release juice.
Sprinkle crystallized ginger and cinnamon over the top of the apples. Do not mix through.
There should be some liquid in the bottom of the pot. If no liquid released from the apples, add 1/4 cup of water or apple juice and mix through.
After mixing, make sure the apples are evenly layered so you cannot see the bottom of the pot.
Carefully sprinkle cornstarch over apples being careful not to let the cornstarch fall through to the bottom of the cooking pot. Do not mix through.
In a medium bowl with a fork, whisk together flour, Bisquick, brown sugar, white sugar, cinnamon, nutmeg and salt.
Using a microplane, grate frozen butter into the flour mixture.
Gently with the fork, mix the butter into the flour mixture, just enough to coat. Do not overmix. You just want crumbles and not for the butter to be combined with the flour, just coated.
Still using a fork, gently mix the Grapenut Nuggets and rolled oats into the topping mixture.
With a light hand, sprinkle the topping evenly over the apples so that you can't see any apples through the topping. Try not to let the topping drop to the bottom of the pot.
Lock on lid and close pressure valve. Cook at high pressure (most machines default to high) for 4 minutes. If you hear or see steam coming from the Instant Pot or pressure cooker and the pressure pin has not popped up, push firmly down on the lid to establish a tight seal. The pressure pin should then pop up.
When beep sounds wait 5 minutes and then release the rest of the pressure.
Turn off pot and remove lid and let the apple crisp sit for 10 minutes before serving.
For a crisper top, use the Mealthy Crisplid at 350 degrees for 4-5 minutes.
Video
Notes
Potato starch or tapioca flour can be used in place of cornstarch.
Frozen Butter
It is best to keep the butter frozen until ready to use. Frozen butter grates very easily with a microplane grater and will incorporate with the flour mixture perfectly without causing large clumps.
Use a Fork
Use a fork to mix the topping. This way, the tiny pieces of butter will be coated with flour and keep them separate, rather than incorporating with the flour and other ingredients in the topping.
Nuts v Grapenuts
If you like nuts such as walnuts or pecansn (and do not have a nut allegery), they can be used in place of the Grapenuts Nuggets. The Grapenut Nuggets add a crunch to the recipe.
For a Hardened Topping
Wait at least 10 minutes prior to serving the apple crisp will allow the topping to harden on its own.
Serve warm with a scoop of ice cream, if desired. A drizzle of Dulce de Leche Recipe {Pressure or Slow Cooker} is wonderful over the crisp.I like to use freshly grated nutmeg and cinnamon, but you can flavor the topping however you like.