01 -
Preheat your oven to 350°F (175°C). Grease a 9-inch pie plate with butter and dust with flour, or use a flour and oil baking spray.
02 -
In a large bowl, cream together the butter, brown sugar, and sugar using a hand mixer until light and fluffy.
03 -
Add the egg and vanilla extract, mixing until well combined.
04 -
Gradually add the flour, cornstarch, baking soda, and salt. Mix on low speed until just combined.
05 -
Stir in the semisweet chocolate chips, mini chocolate chips, and mini marshmallows by hand.
06 -
Press the dough into the prepared pie plate.
07 -
Bake for 20-25 minutes for a gooey center, or up to 30 minutes for a firmer texture.
08 -
Allow the pie to cool to room temperature before slicing into wedges.