Preheat oven to 350° F. Line a 9×9 square baking pan with parchment paper and spray with nonstick cooking spray. Set aside.
Prepare the crust in a food processor. Combine the flour, brown sugar, walnuts and salt and pulse 2 or 3 times to blend. Add the butter and pulse 10 more times until the mixture forms small, coarse crumbs. Press the crumb mixture into the bottom of the prepared pan. Bake 14-17 minutes or until the top feels firm when lightly touched. Set aside.
To make the filling, place a saucepan over medium heat and add the butter, brown sugar and maple syrup. Stir until the butter melts and the brown sugar dissolves. Bring mixture to a boil and let boil for 1 minute. Remove the maple mixture from the heat, let it cool slightly, 5 minutes. Then stir in the chopped walnuts. Pour the hot mixture over the partially baked crust. Using an offset spatula, spread evenly and then sprinkle the cranberries on top.
Bake 25-30 minutes, or until the center is set when the pan is gently shaken.* Let cool for 1 1/2 hours.
Using the ends of the parchment liner, lift the cranberry walnut square and the liner out of the pan. Remove parchment paper. Using a large, sharp knife, cut into 25 bars. Store in an airtight container.
Notes
*While baking, the filling will bubble–don’t worry! It is supposed to do this. The bubbles will become smaller and peter off toward the end of baking.