Line an 8-inch square pan with foil, and spray the foil with butter spray.
In a large saucepan, combine butter, brown sugar, and evaporated milk.
Bring to a rolling boil over medium-high heat, and cook for 8 minutes, stirring frequently. Set a timer for 8 minutes.
Remove from heat, and stir in the maple extract, vanilla, salt, and powdered sugar.
Quickly transfer to a large mixing bowl, and beat for 2-3 minutes, or until it's smooth and shiny.
Fold in 1 c. walnuts and the toffee bits (toffee bits are optional).
Immediately spread into the prepared pan, and sprinkle with remaining walnuts, pressing down lightly.
Cool completely.
Lift the fudge out of the pan using the foil edges, and remove foil.
Cut into bars, and enjoy!