In a bowl, cream together the butter, granulated sugar, and brown sugar until light and fluffy. Add the egg and vanilla and mix until smooth. Stir in the flour, salt, and leavening until a soft dough forms. Add in the chocolate chips if using.
Roll or press the dough into a rectangle inside a piece of parchment paper. If the dough feels too soft, chill it for 20-30 minutes, so it is easier to shape into fry-like strips.
Slice it into thin fry-shaped strips.
Place them on a parchment-lined baking sheet with a little space between them so they bake evenly.
Bake until the edges are lightly golden, and the centers are just set.
Let them cool on the pan briefly. Dust with powdered sugar if desired and serve with dipping sauces.