Preheat oven to 350. Add butter, brown sugar, and white sugar to a bowl. Mix for a couple minutes. Add egg and vanilla and mix again.
Add flour, cornstarch, baking soda, and salt, and mix. If the dough is sticky, add 2 tbsp more of flour.
Add chocolate chips and strawberries and gently mix in. Scoop 2 tablespoons of dough using your hands or a cookie scoop. Place up to 12 dough balls on a normal sized baking sheet that is lined. Bake for 9-12 minutes. Enjoy!