Add the butter to a large mixing bowl and beat until smooth and creamy. Gradually add half of the powdered sugar, mixing until combined and smooth. Stir in vanilla extract and 3 tablespoons of cream. Add the remaining powdered sugar and continue mixing until fully combined and smooth. Adjust consistency by adding more cream as needed. Add salt to taste starting with less than 1/8 teaspoon to balance the sweetness.

Divide the buttercream into 4 bowls. Color two bowls with green and red gel icing, leave one white, and color the last brown.

Fit a large piping bag with Ateco 847 tip and fill with green buttercream. Pipe a large, tall swirl on each cupcake starting from the outer edge, moving inward in three full rotations, finishing with a small peak. Add star and colorful nonpareil sprinkles to the fresh buttercream before it crusts.

Use food writing pens to draw eyes, nose, and mouth on marshmallows beforehand. Fit a large piping bag with Ateco 808 tip and fill with white buttercream. Pipe a flower-like design with petals circling the cupcake’s edge, then smooth the top with an offset spatula. Attach the marshmallow snowman face near the back, add large nonpareil sprinkles as buttons.

Melt 4 oz of chocolate and pipe antlers onto parchment paper. Let dry completely. Fill a large piping bag fitted with Ateco 808 tip with brown buttercream and pipe a short, flat swirl offset toward the front of the cupcake. Attach the red nose sprinkle and place eyeball sprinkles for eyes above, and affix the dried chocolate antlers at the top.

Fill a large piping bag fitted with Ateco 808 tip with red buttercream. Pipe a tall swirl starting wide at the outside edge and spiraling inward for three rotations, finishing with a small peak. Pipe dollops of white buttercream around the base of the red swirl. Pipe a fluffy white ball on the top of the swirl to complete the Santa hat.

Serve cupcakes at room temperature soon after decorating. They can be kept at room temperature up to 24 hours or refrigerated for 3-4 days in an airtight container.