Begin by preparing your workspace - line a baking tray with parchment paper and lightly coat with cooking spray to prevent sticking.
Gently melt butter in a large pot over low heat, careful not to overheat or brown it.
Set aside 2 cups of marshmallows, then add the remaining marshmallows to the melted butter. Stir constantly over low heat until completely melted and smooth.
Remove from heat immediately and stir in vanilla extract and salt until well combined.
Fold in Rice Krispies cereal until evenly coated, then add reserved marshmallows and nonpareil sprinkles. Continue folding until everything is well distributed.
Spread mixture into prepared pan, pressing gently to create an even layer.
Allow treats to cool and set for 30-45 minutes before cutting into bars.
Melt chocolate wafers using a double boiler or candy melting pot until smooth.
Dip the top of each bar in melted chocolate and place on a lined baking tray.
Add pretzel antlers, candy eyes, and an M&M nose before the chocolate sets.
Create scarves using melted red candy melts in a piping bag, allowing them to cool slightly before piping.
Let treats set completely for about 15 minutes before serving.
Notes
Spray your hands lightly with cooking spray when pressing the mixture into the pan to prevent sticking.
Keep heat low when melting marshmallows to prevent them from getting too tough.
Don't compress the mixture too firmly, or the treats will become dense
Work quickly when adding decorations so the chocolate doesn't set before you're finished
Let red candy melts cool slightly before piping, or they'll run too quickly
Cut bars into even sizes for a consistent look
Have all decorations ready before starting the chocolate dipping process
Keep extra chocolate melted in case you need to touch up any spots