Preheat the oven to 400 degrees and have a 2 ½ – 3-quart casserole or 13×9 baking dish standing by.

Peel, core, and chop the apples into medium size pieces (approximately ¾ inch thick and 1 ½ – 2 inches long). Then toss the apple pieces with the tapioca starch, brown sugar, and cinnamon. Turn the coated apples into the waiting baking dish.

Measure the oats, flour, cinnamon, nutmeg, and sugar into a medium mixing bowl and give them a couple stirs with a fork to combine. Cut the butter into small pieces and use your fingers to work the butter into the flour mixture. Working as quickly as possible to keep it cold, crumble the butter and flour together until the butter is broken into tiny pieces no bigger than a small pea. Stir the minced walnuts into the flour and butter mixture then sprinkle the topping over the apples in an even layer.

Place the dish in the preheated oven and bake for 40-45 minutes until the apple juices are caramel colored and bubbly.

Allow the crumble to cool for an hour or more before serving the juices will thicken as they cool wrapping the apples in a cinnamon-infused caramel-like syrup worth waiting for.