1. Line a baking sheet or large plate with parchment paper and set it aside.

2. Add the walnuts to a large skillet over medium-low heat and toast them for 3 to 4 minutes, stirring often, until fragrant. Remove them temporarily from the pan.

3. In the same skillet, add the butter, brown sugar, granulated sugar, water, cinnamon, and salt. Stir until the butter melts and the mixture becomes smooth.

4. Let the sugar mixture bubble gently for 2 to 3 minutes, stirring often, until it looks glossy and slightly thickened.

5. Return the walnuts to the skillet and stir well so every piece is fully coated in the toffee mixture.

6. Remove the skillet from the heat and stir in the vanilla extract.

7. Quickly spread the walnuts onto the prepared parchment in an even layer, separating them with two forks if needed.

8. Let them cool completely until crisp, then break apart any clusters and serve or store in an airtight container.