Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a mixing bowl, whisk together the flour, baking soda, salt, and cinnamon.

In another bowl, mix the prune juice, brown sugar, granulated sugar, egg, and vegetable oil until well combined.

Gradually add the dry ingredients to the wet ingredients, stirring until just combined.

Fold in the walnuts and chocolate chips if using.

Drop tablespoonfuls of dough onto the prepared baking sheet, spacing them about 2 inches apart.

Bake in the preheated oven for 10-12 minutes or until the edges are lightly golden.

Allow cookies to cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.