Step 1

Arrange a rack in the middle of the oven and heat the oven to 325ºF.

Step 2

Place 4 tablespoons salted margarine or butter in a 9x13-inch baking pan. Bake until melted, about 5 minutes.

Step 3

Remove the baking dish from the oven and tilt the pan as needed so the melted butter coats the bottom. Add the ingredients in the following order, do not stir: Sprinkle 1 cup graham cracker crumbs in an even layer, then sprinkle with 1 cup flaked coconut. Sprinkle with 1 cup chocolate chips, then 1 cup butterscotch chips. Pour 1 (14-ounce) can sweetened condensed milk evenly over the top. Sprinkle with 1 cup chopped nuts.

Step 4

Bake until golden brown on top and the center is set, about 30 minutes. Place the pan on a wire rack and let cool completely, about 2 hours. Run a knife around the edges to loosen. Cut into 24 squares.