Preheat the oven to 350°F (175°C). Line a large baking sheet with parchment paper.
In a large bowl, cream together the softened butter, granulated sugar, and light brown sugar until light and fluffy, about 3 minutes.
Add the egg and vanilla extract to the butter and sugar mixture and beat until combined.
In a separate bowl, whisk together the all-purpose flour, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the semi-sweet chocolate chips evenly into the dough.
Spread the cookie dough evenly and thinly over the prepared baking sheet, about 1/8 inch thick.
Bake in the preheated oven for 18 to 20 minutes, or until the edges are golden brown and the center is set and crisp.
Remove from the oven and allow the cookie brittle to cool completely on the baking sheet.
Once cooled, break the cookie brittle into pieces and serve or store.