Preheat the oven to 350 degrees F. Spray 8x8-inch pan with nonstick spray and then line the bottom with parchment paper.
Heat the butter in a small saucepan over medium heat until it browns and begins to smell nutty (watch it closely so it doesn’t burn). Let the butter cool for a few minutes, until just barely warm.
In a large mixing bowl, combine the browned butter and sugars. With a wooden spoon, stir in the egg, vanilla and salt. Stir in the flour, coconut and M&M’s until the batter is blended.
Pour the batter into the prepared pan and smooth the top with a rubber spatula. Sprinkle a few additional M&M’s on top. Bake 25 to 30 minutes. Let the blondies cool before turning them out onto a cutting board and slicing into squares. (Chilling them will make that process even easier.)
Notes
Use chocolate chips in place of M&M’s if you’d like.
For slightly gooey, underbaked blondies, bake for 25 minutes. For fully baked blondies, bake the entire 30 minutes.