Mix together the melted butter and egg. Then stir in the muesli, flour, bicarbonate of soda, sugar and milk. Use your hands to make the mixture into a dough. Grease and flour a baking sheet.
Use a bit of flour to roll out the dough, or if you prefer, roll the dough out between two sheets of baking parchment. Flour the cutters and cut out the letters. For the ‘O’, substitute a round cutter and a very small heart cutter, from a set.
Transfer to the prepared baking sheet and chill for 30 minutes.
Pre-heat the oven to 180°c/ fan 170°c/ Gas Mark 5. Bake the biscuits for 10 - 12 minutes. Transfer to a rack to cool.
For the icing, mix together the icing sugar and egg white. Divide this up into 3 bowls, and colour each bowl with your chosen colours. Spoon the icing into icing bags, and use straightaway or store until ready to use.
When the biscuits are cool, spread over the base colour. Allow this to dry for 10 minutes, before piping on top of it, otherwise the icing will bleed into each other. Decorate with spots, stripes, squiggles or any other pattern.
Present to your mum!