The recipe can be used as a crumble topping or a crust. For a crust, just press it in the pan bottom for a delicious, crunchy oat crust.
Recipes from The Four and Twenty Blackbirds Pie Book by Emily Elsen and Melissa Elsen. Copyright © 2013 by Emily Elsen and Melissa Elsen. Used with permission by Grand Central Publishing. All rights reserved.
Stir together all the ingredients except the butter in a large bowl. Sprinkle in the butter pieces and toss to coat. Rub the butter into the dry ingredients with your fingertips until the butter is incorporated and the mixture is chunky but not homogenous.
If using for a crumble top, chill for at least 15 minutes before using. If using as a crust, press evenly into the bottom and up the sides of an ungreased, preferably metal 9-inch pie pan.
Freeze until solid, about 15 minutes.
Meanwhile, preheat the oven to 350 degrees. Bake on the middle oven rack for 18 to 20 minutes. If the crust slumps or cracks while baking, gently push the crumble back into place, while hot, with a clean, folded kitchen towel. Cool completely before filling.
The crust will keep refrigerated for 5 days or frozen for 1 month.