Butter an 8×8-inch or 9×9-inch square pan. Line with parchment paper or foil, and butter that, set aside.

In medium saucepan, combine the brown sugar, evaporated milk and two sticks of unsalted butter. Bring to a full boil over medium heat. Reduce the heat slightly (no lower than medium-low) and boil for an additional 10 minutes, stirring constantly.

Remove from the heat and stir in the 2 cups powdered sugar, vanilla extract and maple flavoring. Transfer the mixture to a large bowl. (Mixture will be extremely hot. Be cautious) Using a hand mixer beat the fudge on medium speed until thick and glossy-about 3 minutes. Fold in pecans and walnuts and pour mixture into the prepared pan.

Let the mixture cool to room temperature, then cover tightly and refrigerate overnight.

Slice the fudge into 1 inch squares and serve. *Fudge can also be stored in an airtight container at room temperature.*