Prepare the baking dish with nonstick spray or parchment paper.
Toast the walnuts: Place the walnuts on a paper towel and toast in the microwave for 1 minute. Toss, and toast again for 1 minute. Repeat until toasted. Allow to cool and then chop into small pieces.
Toast the coconut: Use the microwave method and toast on a paper towel, turning every 1-2 minutes until toasted.
In a large mixing bowl, combine the graham cracker crumbs and melted butter until mixed.
Press the graham cracker crumbs mixture into the bottom of a 9x13" baking pan, spreading to the corners and pressing down firmly.
Spread both kinds of chocolate chips over the crust in an even layer.
Top the chocolate chip layer with the chopped toasted walnuts.
Spread the shredded toasted coconut flakes over the top of the walnuts in an even layer.
Pour the sweetened condensed milk over the layers, making sure it covers all areas evenly.
Bake for 25 minutes. The coconut on top will be a toasted golden brown.
Remove from oven; cool. Cut into squares and serve on a platter.