Preheat oven to 350.
Cream the butter, coconut oil and sugar.
Add eggs one at a time, beating until incorporated.
Add the flour, baking powder, cornstarch & salt and combine.
Stir in chocolate chips.
Divide dough in half. (freeze one half for later use, or make 2 pizookies.)
Oil a 12-inch skillet and press dough evenly to the edges.
Bake 20-25 minutes, or until lightly browned on top.
Remove from oven and turn on the broiler.
Place Rolos on the hot pizookie.
Top with marshmallow halves.
Return pan to oven to toast the marshmallows under the broiler. Watch carefully, it will take less than a minute. The marshmallows will burn very quickly if left too long.
Cool and cut into slices.