Bring sugar, cocoa, salt, and water to a boil. Cook and stir with a whisk for 2 minutes.
Lower to simmer and stir in milk gradually.
Remove mixture from heat and stir in vanilla.
Whisk until frothy.
For the marshmallow snowman, cut a slit in the middle and turn it around to pipe eyes and a mouth with chocolate syrup. Cut a slit in the middle and press in a biscuit stick for the nose. Press 2 biscuit sticks in the sides of another marshmallow for arms and add 2 dots of chocolate syrup for buttons.
On another marshmallow, press in 2 more biscuit sticks as the legs.
Place the marshmallow snowman on your hot chocolate and serve immediately.