Begin by combining dry ingredients (first 6 ingredients). Set aside
Cream butter and sugars together in a stand mixer with the paddle attachment (or with a hand mixer).
Once well combined, add in eggs and vanilla.
Slowly add dry mixture to wet, continue mixing until fully incorporated.
Add 3/4 c. of the chocolate chips and mix gently until well dispersed.
Scoop cookie dough with a cookie scoop onto a baking sheet lined with parchment paper. I recommend a 2 tbsp. cookie scoop for a regular cookie and 3 tbsp. cookie scoop for a large cookie.
Next, you need to cut your cookies to get the marshmallow inside. Slice a scooped cookie dough ball in half, horizontally. Using your fingers, make a small indentation in each half to put marshmallows in.
For a 2 tbsp. cookie scoop, put 2-3 mini marshmallows in. For a 3 tbsp. cookie scoop, put 3-4 mini marshmallows in. Press the marshmallows in, then add the top back on.
Seal the two halves of the cookie together so all the marshmallow is covered.
It takes a little time, but do this with all the remaining cookie dough balls. Once they're all stuffed with marshmallow, refrigerate for 20 minutes.
Meanwhile, heat the oven to 375 degrees (F). Line a baking sheet with parchment paper or a silpat mat (you really need a lined pan for these or the marshmallow will stick).
Once dough has chilled, place 9-12 cookies on the prepared baking sheet, depending on size.
You will be cooking them for a short time, then opening the oven, putting a couple marshmallows and chocolate chips on top, then closing the oven and cooking for a couple more minutes. See below for times based on your cookie size:
- 2 tbsp. cookie scoop: bake for 5 minutes, then carefully use the back of a spatula to press the down. This will allow the cookie to be more round, and the top to crack a bit and let some marshmallow out. Then top with marshmallows and chocolate chips, then cook for 3-4 more minutes, until marshmallows and chocolate are melted
- 3 tbsp. cookie scoop: bake for 7 minutes, then carefully use the back of a spatula to press the cookie down. This will allow the cookie to be more round, and the top to crack a bit and let some marshmallow out. Then top with marshmallows and chocolate chips, then top, then cook for 4-5 more minutes, until marshmallows and chocolate are melted
Remove from oven when marshmallows and chocolate are melted. They will look a little underdone and be soft in the middle from the marshmallow.
If you don't cool off the cookies right away, the marshmallows in the middle can cook into the cookie. They will still taste amazing in there - it will give it a delicious chewy texture.
However, if you'd like to keep the marshmallow in the middle gooey, be sure to not over cook the cookies, then chill the pan or put it on an iced baking sheet when it comes out of the oven. This will keep the inside from continuing to cook.
Once cookies are set, remove from pan and enjoy! (Tip, I like to cool these on the pan rather than on a cooling rack - they are so gooey inside right when they come out, the baking pan will be a bit more sturdy to hold them until they set.)