Preheat the oven to 350 degrees.
Prepare your brownie mix according to the directions on the box.
Grease the brownie pan
Pour batter equally into the 12 cavities of the pan.
Bake for 20-25 minutes, or until a toothpick comes out clean when inserted.
Remove from the oven, and allow to cool completely, then remove from the pan.
Place brownies on parchment paper and place one marshmallow in the center of the brownies.
Pour white chocolate into a microwave safe bowl and heat in 1 minute increments, until fully melted, stirring well between each heating session.
Using a spoon, drizzle the melted white chocolate over the top of the marshmallow, and onto the brownie.
Refrigerate for 10 minutes once you’ve completed the step above on all brownies.
Place semi sweet chocolate into the corner of a ziplock baggie and heat in the microwave for 45 seconds. Remove and massage with your hand to help melt all of the chocolate. If not fully melted, heat for an additional 20 seconds, and massage again.
Snip the opposite corner off the baggie, and insert the piping tip, and move chocolate to that side of the baggie.
Gently squeeze chocolate through the piping tip to make one dot for each of the eyes, and an oval for the mouth.