This particular cookie was built on top of a store bought sandwich cookie, but my end goal will be to use NFSC.

I really want the face to have a 3D look, but found the thickness of MMF needed to accomplish that look, resulted in way too much MMF from a 'taste' perspective.

So, I'm hoping you can give me some ideas on how to bulk out the MMF with something that would go well with MMF and NFSC. I'm thinking I could intentionally leave a hollow in the MMF when sculpting it, then maybe spoon in melted chocolate, caramel or marshmallow, and once it is set, put it on the cookie.

FYI - these cookies are just for fun, and I'm not concerned with the time involved for the process. Cookies are my new hobby.

I would go with mini marshmallows cut in half.

I did that on wreath cookies and then covered with melted white chocolate. You'll want to use something to make the mm's stick to the cookie before you add the fondant.