Preheat oven to 350°F (175°C). Grease a 9”x 13” x 2" baking pan, and line with parchment paper so that the ends overhang by a couple of inches on the two short ends.
Whisk together the flour, brown sugar, and salt. Add the butter and mix using a pastry blender or a fork until combined. The mixture will be crumbly but will hold together when pinched.
Press the crust mixture evenly into the bottom of the prepared pan.
Bake for 15 minutes or until the edges are lightly browned. Set aside.
To make the filling:
Place the eggs in a large bowl and beat lightly. Add the maple syrup, melted butter, brown sugar, sugar, and salt, stirring until combined. Stir in the nuts.
Pour the filling over the partially baked crust. Bake 30 to 35 minutes, or until the filling is set.
Cool the bars completely in the pan on a wire rack. Once cool, use the overhanging parchment paper to lift the bars out of the pan and onto a cutting board and cut into bars.
Notes
Store in an airtight container at room temperature up to 3 days.