10tablespoonscold butter, in 1/2" dice(5 ounces, 1 1/4 sticks)
1 1/2cupscoarsely chopped raw walnuts
Apple filling:
4 1/2poundsapples (12 - 15 medium-large, such as pink ladies, fujis or golden delicious; or half and half granny smiths and McIntosh), peeled, cut off the core and sliced crosswise 1/4" thick (12 cups)
1teaspoonlemon zest (from 1 lemon)
3tablespoonslemon juice (from 1 - 2 lemons)
1/2cuplight brown sugar
1/8teaspoonsalt
Instructions
Make the topping:
In the bowl of a food processor, grind the oats to a floury consistency. Pulse in the brown sugar, cinnamon, nutmeg and salt to combine, then pulse in the butter until the mixture looks like coarse meal, with no large butter chunks remaining, about 10 four-second pulses. Add the nuts and pulse several more times until the topping looks like 'slightly clumpy wet sand'. (Cook's warns: Don't over-mix, or the texture will be too wet and homogenous.) Chill the mixture in the fridge while you get on with the fruit, at least 15 minutes or up to several days.
Make the apple filling and bake the crisp:
Position a rack in the lower third of the oven and preheat to 375ยบ. Have a 9x13" glass baking dish (or the equivalent) at the ready.
Peel the apples if you like, cut them off the core and then slice them crosswise 1/4" thick. (Alternately, you can use a dandy corer-peeler-slicer, then cut the peeled, cored, sliced apples into quarters.) Toss the apple slices in a large bowl with the lemon zest, lemon juice, brown sugar and salt to combine.
Lay the apple mixture in the pan, sprinkle the topping over (don't press down) and bake until the apples are bubbling thickly and the topping is golden brown, about 55 minutes. Serve warm with generous scoops of ice cream.
The crisp can hang out at room temp for several hours, then be reheated before serving. It is best the day it is baked, but you can keep leftovers in your fridge, reheating in the oven or toaster oven.
Notes
Adapted generously from Baking Illustrated.This makes enough crisp to fill a 9 x 13" baking dish; feel free to halve the recipe and bake the crisp in an 8" square pan. The topping can be made ahead and stored in the fridge for up to a few days.Feel free to add a cup or two of blackberries, huckleberries, cranberries, plums or thinly sliced rhubarb to the apples; you may need to adjust the sweetness for tart fruit. Cook's says you can substitute 5 - 6 pounds of ripe pears or plums, or 6 pounds of peaches, for the apples. If using plums, or peaches mixed with berries, add 2 tablespoons quick-cooking tapioca to the fruit mixture.If you lack a food processor, you can grind the oats in a coffee grinder, or use purchased oat flour, and work in the butter with your fingertips or in a stand mixer fitted with the paddle attachment. A corer-peeler-slicer makes quick work of the apples, should you have one.Nutritional values are based on one of ten servings.