To make this crust in a food processor, combine nut halves or pieces with the butter, sugar, and salt and pulse until the nuts are finely chopped.
Preheat the oven to 375°F. Grease a 9- or 10-inch pie pan or an 8- to 10-inch springform pan.
Chop to the consistency of coarse crumbs:
      2 cups walnuts or pecans
Add and mix with a fork until uniformly moistened:
      4 tablespoons unsalted butter, softened
      3 tablespoons sugar
      1/4 teaspoon salt
Using your fingertips or the flat bottom of a drinking glass, press the mixture evenly over the bottom and sides of a pie pan or over the bottom and 1/2 inch up the sides of a springform pan. Bake until the crust is richly browned, 10 to 15 minutes. Check periodically during baking; if the crust has slipped down the sides of the pan, smooth it into place with the back of a spoon. Let cool before filling.