Oh, poor pear crisp -- apples and summer berries take all the crisp centerstage and you're in the shadows all the time. Well, I just want you to know that I know. I know that, made right -- with just cooked pears, a crisp, toasty topping, and lots of warm spices -- you're the best crisp of them all.
cut into small dice and divided plus more for coating the dish
Heat oven to 400°F and arrange a rack in the middle. Coat an 8-by-8-inch (or other 3 quart) baking dish with the extra butter and set aside.
For the pears: Cut the pears in half, core them, then cut them into 3/4-inch dice. Combine pears with the lemon juice in a large, nonreactive bowl and toss to coat. Sprinkle with 1/4 cup of the flour, 1/3 cup of the brown sugar, and half salt and toss to coat. Turn the mixture into the prepared baking dish then scatter 2 tablespoons of the diced butter over the top.
For the topping: Place the remaining 1/4 cup flour, 1/3 cup light brown sugar, and in a medium bowl, add the remaining 1/4 cup (1/2 stick or 4 tablespoons) butter, all the gingersnap crumbs, and the walnuts, and mix together until evenly mixed and the mixture clumps together when squeezed. Sprinkle the topping over the pears and bake until the pears are fork tender and the topping is browned, about 25 to 30 minutes. Let sit at least 20 minutes before serving.