1. In a medium bowl, whisk together the flour, cornstarch, baking soda, and sea salt. Set aside.
2. In a large bowl, whisk together the melted butter, brown sugar, granulated sugar, lactose-free yogurt, and vanilla extract until smooth.
3. Add the dry flour mixture into the wet ingredients. Fold using a spatula until a dough forms.
4. Fold in the chocolate chips.
5. Cover and chill the cookie dough in the fridge for at least 30 minutes.
6. Preheat your oven to 175°C and line a baking sheet with parchment paper. Scoop balls of dough onto the sheet. Bake for 10 to 12 minutes until the edges are light golden brown.
7. Let them cool on the baking sheet for 10 minutes to firm up, then enjoy.