Step 1: Melt the Chocolate - Break white chocolate into small pieces and place them in a microwave-safe bowl. Add a tablespoon of vegetable shortening and heat in the microwave for 30 seconds at a time, stirring well in between, until the mixture is fully melted and smooth. This should take about 1 to 2 minutes in total.

Step 2: Dip the Marshmallow Base - Take a large marshmallow and carefully dip the bottom half into the melted chocolate, allowing any excess to drip off. Place the dipped marshmallow onto a sheet of parchment paper for easy removal later.

Step 3: Stack the Marshmallows - Next, stack two more large marshmallows on top of the dipped one, applying a small amount of melted chocolate between each to act as glue. Gently press down to secure each marshmallow in place.

Step 4: Coat the Marshmallow Structure - Once the marshmallow stack is stable, carefully coat the entire structure with the remaining melted chocolate using a spoon or spatula. Place the coated marshmallow back on the parchment paper and let it set until the chocolate is firm, approximately 10 to 15 minutes.

Step 5: Add the Candy Eyes - While the chocolate is still slightly tacky, attach candy eyes to your Ghostbusters Stay Puft Marshmallows by gently pressing them into the chocolate.

Step 6: Final Touches with Powdered Sugar - After the chocolate coating has set completely, dust the exterior with powdered sugar and use a black edible marker to draw a cheerful smile on the front.

Step 7: Serve and Enjoy - Transfer them to an airtight container at room temperature to keep them soft and fluffy.