Preheat oven to 350 degrees F. Line a large baking sheet with a Silpat baking mat, parchment paper, or aluminum foil. If you are using aluminum foil, spray lightly with nonstick cooking spray. Place graham crackers in a single layer, touching, on the large baking sheet. Set aside.

In a medium saucepan, melt butter and brown sugar together over medium-high heat. Bring butter and brown sugar mixture to a boil. Simmer for 4 minutes, stirring constantly. Pour mixture evenly over graham crackers. Bake for 8 minutes.

Remove the pan from the oven and immediately sprinkle chocolate chips evenly over the top of the graham crackers. Let the chocolate chips sit for 2 minutes so they have a chance to melt. Spread melted chocolate with a knife or rubber spatula. Sprinkle almonds or pecans on top.

Let the graham cracker toffee sit for about 2 hours or until the chocolate hardens. If you are in a hurry, you can refrigerate the toffee for an hour, or freeze for 30 minutes. When chocolate is set up, break the toffee into pieces and enjoy!