The whole pie tastes like the soft, GOOEY, underbaked centers of fresh chocolate chip marshmallow cookies!! Between the melted chocolate, marshmallows, and big time gooey factor, this pie is PERFECT!!
Preheat oven to 350F and spray a 9-inch glass pie plate very well with cooking spray; set aside.
To the bowl of a stand mixer fitted with the paddle attachment or large bowl and electric handheld mixer, beat the butter on low speed until smooth, about 1 minute.
Add the sugars and beat on medium-high speed until creamed and well combined, about 2 to 3 minutes.
Stop, scrape down the sides of the bowl, and add the egg, vanilla, and beat on medium-high speed until light and fluffy, about 2 minutes.
Stop, scrape down the sides of the bowl, and add the flour, corn starch, baking soda, salt, and mix until just combined, about 30 seconds.
Add the chocolate chips and beat for a few seconds on low speed to incorporate.
Add the marshmallows and beat for a few seconds on low speed to incorporate. They may be a little finicky and not want to incorporate but do the best you can to incorporate them.
Transfer dough to prepared pie plate (Tip – Make sure you have some marshmallows at the top for visual appeal and the less you have actually touching the sides or base of the pie dish, the easier your cleanup will be later on) and smooth with a spatula as necessary.
Bake for about 18 to 20 minutes, or until center is just set and marshmallows are just barely golden. Edges will be more set and lightly golden; do not overbake because the pie tastes much better on the gooey side.
Allow the pie to cool until it’s comfortable to eat.
Notes
Pie is best fresh but will keep covered at room temp for up to 5 days.