Add the water, walnuts, butter, sugar, light brown sugar and cinnamon to a saucepan over medium high heat.

Cook the mixture until the liquid has mostly all evaporated, and the walnuts are clinging together.

Stir in the salt.

Transfer the mixture to a parchment lined baking sheet, and press into a single flat later.

The mixture will harden as it cools. Once cool, break apart and serve.