Mix vanilla and oats in a large bowl.
Add honey and then Nutella, and mix well.
Line a baking sheet with parchment paper.
Roll the mixture into about 1.5″ size cookie balls while they’re sticky.
Press a little dot into each cookie ball, and place the marshmallow. These are going to be the eyes, so add as many as you’d like per monster cookie. You may have to reshape the cookie a little around the marshmallow.
Use your candy markers to draw pupils onto the marshmallows. This is where you can be really creative. You can mix and match, add eyelashes, eyebrows, and more.
Store in the fridge.
Remove from fridge a few minutes before serving.