For the topping:
1 1/4 cup old-fashioned oats *
1 cup light brown sugar
3/4 cup flour
1/2 tsp cinnamon
1/2 tsp kosher salt
1 1/2 sticks unsalted butter, cold and cut into 1/2-inch cubes
Combine the oats, brown sugar, flour, cinnamon and salt in the bowl of an electric mixer. Using the paddle attachment, mix on low speed to just combine the ingredients. Add the butter and mix on medium speed until the mixture begins to resemble coarse wet crumbs. (The mixture should hold together loosely if you squeeze it in your hand, but should still easily crumble apart. If you mix it for too long, the ingredients will become too thoroughly incorporated, and the mixture will turn dense like cookie dough, so don’t get carried away.) Cover with plastic wrap and refrigerate until needed. This topping can be stored for 2 days.
For the filling:
4 large Granny Smith Apples, peeled, cored and thinly sliced
4 large Fuji Apples, peeled, cored and thinly sliced
1 Tbl lemon juice
1/4 cup granulated sugar
large pinch cinnamon
Preheat the oven to 375°F. Butter a 9x13 inch glass baking dish.
In a large mixing bowl, stir to combine the sliced apples with the lemon juice. Add the sugar and cinnamon and stir to evenly coat. Transfer the fruit to the prepared baking dish. Sprinkle the topping over the filling. There’s a trick to doing this: Grab a handful of the topping and gently squeeze to make it somewhat stick together, then crumble this mass into coarse pieces, spreading the crumbs evenly over the filling. Bake until the fruit is tender and the crisp topping is golden brown and crisp, about 45 minutes to an hour. Cool about 20 minutes, then serve topped with a scoop of vanilla ice cream.
* By ‘old fashioned oats’ I mean oats that aren’t instant oats. I also don’t mean stone-cut oats. Definitely not those. Old fashion oats will look a lot like the flat, flaky instant oats, but are a little more substantial. I like the brand Bob’s Red Mill, which is pretty easy to find in most good grocery stores. But I don’t think the regular old Quaker Oats brand could be too bad either.