Place buttercream in a piping bag fit with a large round piping nozzle. Working perpendicular to the top of the cupcake, start piping icing in the centre of the cupcake in the shape of a Santa hat, using gradually less pressure to create a cone-like shape.
Cover the buttercream in red coloured sugar or sprinkles.
Use a small star-shaped nozzle to pipe more buttercream around the base of the hat for the white rim. Repeat with remaining cupcakes.
Strawberry Santa hat:
Spread cupcake with buttercream icing. Place a strawberry in the centre, with the tip facing up. Using a small star-shaped piping nozzle, pipe a small bit of icing at the tip for the hat's pompom.
Switching to a large round nozzle, if desired, pipe icing around the base to create the hat's rim. Repeat with remaining cupcakes.
Fondant Santa hat:
Roll out a small piece of red fondant icing to about 3mm thick. Cut into a circle, about 8cm in diameter. Cut out 1/4 of the circle, leaving a Pac-Man shape.
Using a large round piping nozzle, pipe some buttercream into a rough cone shape in the centre of the cupcake to support the hat.
Fold the cut edges of the fondant together to make a cone shape. Place the hat on top of the cupcake, resting over the fondant.
Using a small star-shaped nozzle, pipe icing at the tip of the hat and along the base to create a rim. Repeat with remaining cupcakes.