In the bowl of a mixer, cream the margarine and sugars on medium speed until light and fluffy, about three minutes.

Add the egg and yolk and mix until just combined, about 30 seconds.

Add flour, salt, and baking soda and mix until just combined. Do not overmix!

Fold in the chocolate chips and graham cracker pieces.

Using a scooper, scoop up some dough and press down in the center to create a well in the dough. Place half of a large marshmallow or two mini marshmallows into the cavity.

Release the dough from the scooper and shape into a ball. Place on a lined baking sheet.

When all the cookies are shaped, refrigerate for an hour or overnight.

Bake at 350 degrees Fahrenheit for 12–14 minutes.

Cookies are ready when the edges are beginning to brown and the center is still soft, appearing slightly raw. Remember: the cookies will continue to bake and firm up once they’re out of the oven. Do not overbake. Rather leave them slightly underbaked than risk having a crunchy cookie!