In a food processor, mince 1/3 cup pecans with 1 1/4 cups all-purpose flour and 1/4 cup sugar. Add 1/2 cup (1/4 lb.) butter or margarine, in chunks, and whirl until fine crumbs form. Add 1 large egg yolk and whirl until dough holds together. (Or mince nuts with a knife, then put in a bowl. Rub in flour, butter, and sugar until fine crumbs form; then, with a fork, mix in yolk. Pat into a ball.) In 6 tart pans (4 1/2 in. wide) with removable rims, or an 11-inch tart pan, press dough evenly over bottom and up sides, flush with rims.