Pour walnuts into a skillet over medium heat. Cook, stirring frequently, until lightly toasted, about 3 minutes. Remove from heat and allow to cool.
Line a rimmed half-sheet pan with aluminum foil and spray with nonstick cooking spray.
Combine sugar, water, and golden syrup in a nonstick saucepan over medium heat. Do not stir. Clip a candy thermometer to the side of the pan, and wait for the mixture to reach 275 degrees F (135 degrees C), about 5 minutes.
Once sugar mixture reaches 275 degrees F (135 degrees C), add toasted walnuts. Stir using a silicone spatula until mixture reaches 300 degrees F (150 degrees C), about 5 minutes more. Stir in butter, baking soda, smokehouse rub, and walnut extract.
Remove saucepan from heat and carefully pour mixture onto the prepared baking sheet. Allow to cool before breaking into smaller pieces, about 30 minutes.
