Preheat the oven to 350 degrees F and line a 13- by 9-inch baking pan with parchment, leaving a 2-inch overhang. Or, butter the baking dish well.

Making the crust: The crust is easiest to do in a food processor but simple by hand too. If using a processor, pulse until the graham crackers are finely ground. Then add the brown sugar, baking powder, and salt. Pulse to combine, then add the melted butter and the egg. Continue to process until the crumbs are completely moistened and large clumps begin to form. Transfer the graham cracker mixture into the prepared pan. Using your fingers or the back of a spoon, press the crumbs into the pan creating an even layer. Bake the crust until it is set and dry, about 12 to 15 minutes.

Remove the pan from the oven and pour the sweetened condensed milk evenly over the crust, spreading in an even layer. Then sprinkle the chocolate chips, butterscotch chips, and pecans evenly over the surface. Sprinkle the flaked coconut in an even layer on top. Using the back of a spoon, press lightly over the toppings so they come in contact with the cream layer. This will help bond the cookie bars.

Bake until the toppings are golden brown, about 25 to 30 minutes. Let cool in the pan. To serve, lift the bars out of the pan using the parchment overhang, transfer it to a cutting board and cut into bars using a serrated knife.