Preheat the oven to 180°C/gas mark 4. Line 2 baking sheets with baking paper. Mix the butter and sugar together in a bowl, until pale and creamy.
Sieve the flour into the bowl with the milk. Mix everything together with your hands to make a ball of soft dough – you might need to add more milk.
Sprinkle a little flour over a table. Divide the dough into 4 pieces and roll out 1 piece to a thickness of about 5mm. Using lettershaped cutters, help your little one cut out letters to spell 'I love mum' or another message. Repeat with the remaining dough.
Using a palette knife, carefully transfer the letters to the baking sheets. Bake for 12-14 minutes until the biscuits are just golden. Leave them to cool on the baking sheets for a few minutes before putting them on a cooling rack to cool completely. Let little ones decorate the biscuits using edible glitter writing icing and party sprinkles.