Line a 13x18 rimmed baking sheet with foil and spray with oil.
Lay graham crackers side by side in an even layer to fill the baking sheet perfectly (break pieces if needed). Set aside.
In a medium sauce pan, combine butter and brown sugar. Bring to a boil, and boil for 3 minutes, stirring frequently.
Stir in the vanilla, then carefully pour the mixture over the graham crackers. Use a rubber spatula to spread it, and work quickly before the toffee starts to firm up.
Sprinkle the chopped pecans and cooked, chopped bacon over the top and place in the preheated oven.
Bake for 5-7 minutes, until bubbling.
Remove from oven, cool to room temperature, then transfer the baking sheet to the refrigerator to cool completely (at least 2 hours).
Once chilled, break into pieces and dig in!
*Note: You can store and serve the toffee chilled or at room temperature.