Preheat oven to 350*F degrees.
In a large mixing bowl, beat butter, brown sugar and cane sugar until smooth and cream.
Add egg and vanilla, mix well.
Add the flour in slowly, until mixed well. Then add baking powder and salt, mix at low speed until combined.
Carefully add chocolate chips until mixed with cookie batter.
Scoop out the cookie dough using an ice cream scoop. Place your thumb in th middle to form a cavity and place half a marshmallow inside. Press down, then add other half of marshmallow (optional.)
Release the cookie dough ball from the cookie scoop and roll together so that the marshmallow is almost completely covered by cookie dough. Repeat with remaining dough. Refrigerate cookie dough balls for 30 minutes or up to overnight.
Place cookies 4 inches apart on a cookie sheet lined with parchment paper. Bake at 350*F degrees for 12-18 minutes or until the edges and marshmallow are golden brown, the center will still be gooey.
Allow to cool down....or NOT! Who are we kidding. Cookies are best straight out of the oven.