For the topping:
1/3 cup all-purpose flour or white whole-wheat flour
1/3 cup rolled oats (not instant)
1/3 cup packed dark brown sugar
1/4 teaspoon ground cinnamon
1/4 teaspoon kosher salt
1/2 cup chopped pecans
2 tablespoons melted unsalted butter
For the filling:
1/4 cup maple syrup
2 tablespoons molasses
3 tablespoons all-purpose flour or white whole-wheat flour
1/2 teaspoon ground cinnamon
1/2 teaspoon kosher salt
2 1/2 pounds apples, cored and cut into rough 1-inch chunks
1 tablespoon unsalted butter
Ice cream or whipped cream, for serving (optional)
Make the crisp topping:
Preheat the oven to 350°F.
Whisk the flour, oats, sugar, cinnamon, and salt together in a bowl, making sure to remove any large sugar lumps.
Stir in the pecans, then stir in the 2 tablespoons melted butter until the topping is moist and starting to clump together.
Make the filling:
Whisk the maple syrup, molasses, flour, cinnamon, and salt together in a large bowl. Toss the apples in the bowl, stirring until they're evenly coated; set aside.
Coat the bottom and sides of a 10-inch cast iron skillet or other heavy-bottomed ovenproof skillet with the 1 tablespoon butter. Pour the apple filling into the skillet, including any liquid that may have settled in the bottom of the bowl, and spread into an even layer. Spread the crisp topping evenly over the apples.
Cover the skillet loosely with foil and bake for 30 to 40 minutes, until the apples have softened and the crisp is bubbling around the edges of the pan.
Remove the foil and bake for 15 to 20 minutes more, until the topping is deeply browned.
Let cool for at least 15 minutes before serving. Serve with scoops of your favorite ice cream or generous spoonfuls of whipped cream.