Preheat oven to 350°F (175°C). Grease an 8-inch square baking pan.
In a medium bowl, combine graham cracker crumbs and melted butter. Press into the bottom of the prepared pan.
Pour sweetened condensed milk over the crust. Layer chocolate chips, butterscotch chips, and peanut butter chips over the condensed milk. Sprinkle with pecans.
Bake in preheated oven for 25 minutes, or until golden brown.
Allow to cool completely before cutting into bars.
Interesting Facts
Sex-in-a-Pan is a take on the classic Tres Leches Cake, which is a sponge cake soaked in three kinds of milk.
This dessert is named for its layers, which look like the seven deadly sins.
The origins of this dessert are unknown, but it is believed to have originated in the United States in the 1950s.