Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.
Arrange graham crackers in a single layer on the baking sheet.
In a saucepan, melt butter and sugar together over medium heat, stirring constantly until mixture comes to a boil. Boil for 3 minutes, stirring constantly.
Pour butter mixture evenly over graham crackers. Bake for 5 minutes.
Remove from oven and sprinkle chocolate chips over the hot toffee. Let stand for a minute to melt, then spread evenly.
Let cool completely before breaking into pieces.
Notes
For extra flavor, sprinkle chopped nuts on top of the melted chocolate chips.