When it comes to these Gooey Marshmallow Chocolate Chip Cookies, there's not much that can be said. Extra thick, but soft, these cookies are the perfect sweet treat for any sweet tooth and a glass of milk is far from cliche with this batch.
Using an electric stand mixer (fitted with a paddle attachment), cream together the softened butter and both sugars on medium speed until smooth, about 2 minutes. Next, add the eggs and mix on high until well combined (for another 1 minute). Be sure to scrape down the sides and bottom of the bowl if needed. Finally, add the vanilla extract, mixing everything on high speed until combined. Set aside.
Now, in a large bowl, toss together the all-purpose flour, baking soda, cornstarch, and sea salt. Add the dry ingredients to the wet ingredients and mix on low until fully combined.
Add the chocolate chips and mix for about 5 seconds until well incorporated.
Cover the dough tightly with plastic wrap and chill for at least 1 hour in the refrigerator (or 30 minutes in the freezer).
Remove the cookie dough from the refrigerator and allow it to sit a bit at room temperature (about 10 minutes). Preheat oven to 350 degrees Fahrenheit and line 2 large baking sheets with parchment paper or silicone baking mats.
Once chilled, work the dough with your hands, rolling them into individual balls, about 1.5 Tbsps of dough each.
Then bake the cookies for about 10-11 minutes, until barely golden brown around the edges. **NOTE: About 2-3 minutes before cookies are finished, add marshmallows and chopped chocolate bar pieces to each cookie by gently inserting them.**
**NOTE: They will look extremely soft when you remove them from the oven, but allowing them to cool for 5 minutes on the cookie sheet will make them set.** Next, transfer the cookies to a cooling rack to cool completely.
STORAGE: Cookies stay fresh covered at room temperature for up to 1 week.