1-Preheat your oven to 350°F (177°C) and line baking sheets with parchment paper or silicone mats to prevent sticking.

2-In a medium bowl, whisk together the all-purpose flour, cornstarch, baking soda, and salt.

3-In a large bowl, beat the softened butter with brown and granulated sugars until creamy and smooth.

4-Add the egg, egg yolk, and vanilla extract; mix thoroughly to combine.

5-Gradually add the dry ingredients to the wet mixture, folding gently until combined.

6-Fold in the mini chocolate chips evenly, ensuring the dough is soft and sticky.

7-Use a cookie scoop or spoon to portion about 1.5 tablespoons of dough per cookie onto the baking sheets, spacing them about 3 inches apart. Slightly flatten the dough balls to create a flatter cookie shape.

8-Bake for 12-13 minutes until the edges are lightly browned and the centers remain soft.

9-Allow cookies to cool on the baking sheet for 5 minutes; optionally press extra mini chips onto the warm tops. Then transfer to wire racks to cool completely.

10-To assemble, place one cooled cookie upside down, add about 1/4 cup of ice cream, spreading gently to the edges. Top with another cookie and press lightly in the center.

11-Roll the edges of the sandwiches in mini chocolate chips, sprinkles, or chopped nuts if desired.

12-Wrap each sandwich tightly in plastic wrap or parchment paper and freeze for at least 3 hours or up to 3 months to firm up before serving.