To make the dough, beat the butter and sugar together to get a creamy texture.
Add the egg and beat again well.
Sift in the flour, add the vanilla extract, and use your hands to make a dough.
Cover it with clingfilm and chill it in the fridge for 20 minutes.
Use a rolling pin to roll the dough, then cut out shapes with a heart-shaped cookie cutter.
Arrange the cookies on 2 or 3 baking trays lined with non-stick paper, and bake in the preheated oven at 180 degrees Celsius *350 Fahrenheit) for 9-10 minutes until pale golden around the edges.
Leave the cookies to cool down completely.
To make the icing, sift the icing sugar, add the milk and red food colouring, and mix well into a smooth paste.
Transfer the paste to a piping bag fitted with a small circle nozzle, and decorate each cookie, then add the sprinkles.
Leave the icing to set completely before serving or storing.