The oven should be already heated to 350°F.

Melt the butter, margarine, and brown sugar in a heavy 2-quart or larger saucepan over low heat, stirring from time to time. Meanwhile, spray the bottom and sides of a baking pan, preferably a 15 X 10-inch jelly-roll pan, with cooking oil spray. Line the pan with a single layer of graham crackers, using as many whole ones or pieces as you need to cover the pan bottom.

When the butter and margarine are melted, raise the heat to medium and bring the mixture to a boil. Boil 1 minute, stirring constantly. Reduce the heat to low and continue to cook, stirring constantly, for 1 minute more, until the mixture is well blended. Remove from the heat and continue to stir until the mixture stops bubbling. Stir in the chopped pecans.

Spoon the caramel mixture over the crackers. (Don't worry if all of the crackers are not completely covered. The caramel will spread during baking.) Bake for 8 minutes. Remove from the oven and cool for 15 minutes. Use a spatula to remove the cookies to a wire rack. (They should come apart in their original, whole shape.) Cut or break the pieces in half while still warm. Cool 5 minutes more (or until room temperature) and serve.