For this recipe, I brown the butter in the crust, so the cookies have a toasty, rich nuttiness. In homage to my hippie Vermont roots, I also added a bit of pure maple syrup to the sticky coconut layer to give it a more complex flavor and hit of nostalgia.
- Prepare an 8- inch square cake pan with greased aluminum foil that completely covers the pan and goes up the sides, then line with a parchment-paper sling.
- Preheat the oven to 350°F / 175°C.
- In a large bowl, whisk together the brown butter and yolk until combined. Add the brown sugar, flour, and salt. Blend with a spoon or your fingers until it is uniformly mixed. It may be a bit crumbly, but not dry. Distribute the dough evenly and press it into the prepared pan. Cover with plastic wrap so you can easily smooth it.
- Freeze until solid, about 5 minutes. Bake in the middle of the oven for 12 to 15 minutes, until the crust is golden brown. Allow the crust to cool on a rack while you make the filling. Leave the oven on.
- In a large bowl, whisk together the maple syrup, condensed milk, vanilla, egg white, salt, and pumpkin pie spice. Stir in the coconut, chocolate, and nuts. Spread the mixture over the baked crust.
- Bake in the middle of the oven for 30 to 35 minutes, until the topping turns golden brown.
- Cool slightly before removing from the pan. Cool completely on a cooling rack before cutting into bars.