1.4 kilograms Honeycrisp apples, peel cored and diced (8 cups)
1/3 cup water
1/3 cup lemon juice
1/3 cup granulated sugar
1 tablespoon ground cinnamon
1/8 teaspoon ground allspice
3 cups all-purpose flour
3 cups quick cooking oats
2 cups dark brown sugar
2 teaspoons baking powder
1 teaspoon salt
1-1/2 cup butter room temperature butter
Preheat oven to 350F.
Line a rimmed baking sheet with parchment paper, ensuring the parchment comes up the sides of the baking sheet.
Add apples, water, lemon juice, sugar, cinnamon and allspice to a medium pot and bring to a simmer. Cook for 15 minutes, stirring often until apples are soft. Remove from heat.
Into a large bowl add the flour, oats, brown sugar, baking powder and salt. Stir to combine all the ingredients. Add the butter and work it into the dry ingredients by rubbing the butter and dry mixture between your fingers. Butter should be incorporated fully with some pea sized pieces left.
Use a cup measure to distribute six cups of the crumble mixture evenly over the prepared baking sheet. Use your hands to press down firmly, creating and even and compact base. Place in the oven for ten minutes.
Remove base from oven and pour the apple mixture over the base. Use a spatula to spread the apple mixture over the entire surface of the base.
Top the apples evenly with remaining three cups of crumble. Press the crumble top down gently but firmly.
Return to the oven and cook for 45-55 minutes until golden brown.