Line a baking sheet with foil. Butter the foil; set baking sheet aside.
In a small heavy skillet combine coarsely chopped pecans, sugar, and butter or margarine. Cook mixture over medium-high heat, shaking the skillet occasionally until sugar begins to melt. Do not stir the mixture. Reduce heat to low and continue cooking until sugar is golden brown, stirring the nut mixture occasionally.
Remove skillet from the heat. Pour nut mixture onto the foil-lined and buttered baking sheet. Cool completely. Break the nut mixture into small chunks. Store the coated nuts, tightly covered, for up to 1 week. Makes 3/4 cup (4 servings).