01 - Preheat oven to 350°F. Line a baking sheet with parchment paper.
02 - In a mixing bowl, combine the maple syrup, cinnamon, salt, and vanilla extract if using, whisking until smooth.
03 - Add the walnut halves to the bowl and toss until every piece is thoroughly and evenly coated with the maple-cinnamon mixture.
04 - Spread the coated walnuts in a single even layer on the prepared baking sheet, making sure they are not crowded together.
05 - Bake for 12 to 15 minutes, stirring once halfway through, until the walnuts are glossy, fragrant, and the glaze has caramelized.
06 - Remove from the oven and let the walnuts cool completely on the baking sheet. The maple glaze will harden and set as they cool.
07 - Transfer the cooled walnuts to an airtight container and store at room temperature for up to 1 week.