Preheat oven to 350°F. Line a baking sheet with parchment paper.

In a medium bowl, whisk together the flour, baking powder, baking soda, cinnamon, and salt. Set aside.

In a large bowl, whisk together the melted butter and brown sugar until combined. Whisk in the egg and vanilla extract.

Stir in the dry ingredients until just combined. Fold in the chocolate chips and walnuts, if using.

Drop the cookie dough by the tablespoonful onto the prepared baking sheet. Bake for 10-12 minutes, or until the edges are golden brown.

Let the cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.