Adjust an oven rack to the lower-middle position and heat oven to 350°F.
Line a 9x13-inch baking dish with aluminum foil and spray lightly with nonstick cooking spray.
In a medium nonstick skillet over medium heat, toast the coconut, stirring occasionally until lightly browned and golden. Remove from heat.
1 cup sweetened flaked coconut
Place the graham crackers in a large resealable plastic bag and crush with a rolling pin to create multiple sizes of crumbs.
5 ounces graham crackers
Meanwhile, place the sticks of butter into the prepared baking pan and put it in the oven to melt the butter, about 6 minutes. When the butter has melted, remove the pan from the oven. Add the graham cracker crumbs and toss lightly with a fork until all the butter is absorbed and the crumbs are evenly distributed over the bottom of the pan.
8 tablespoons unsalted butter
In order, sprinkle the chocolate chips, white chocolate chips, butterscotch chips, and the toasted coconut over the graham cracker crumbs. Pour the condensed milk evenly over the entire baking pan.
1 cup semisweet chocolate chips, ½ cup white chocolate chips, ½ cup butterscotch chips, 14 ounces canned sweetened condensed milk
Return the pan to the oven and bake until the top is golden brown, about 25 minutes. Remove pan from oven and cool on a wire rack until room temperature, about 2 hours. Remove bars from the pan using the foil and transfer to a cutting board. Cut into bars using a sharp knife.
Notes
Source: Annie's Eats, originally adapted from Baking IllustratedYou're Gonna Bake It After Allbakeitafterall.com