Children of all ages can help form the batter into balls and then flatten gently with a fork.
Preheat the oven to 190°C/gas mark 5. Line two baking sheets with baking parchment.
In a large bowl, cream together the butter and sugar. Add the egg and beat until well combined. Stir in the vanilla extract.
In another large bowl, combine the flour, oats, baking powder and bicarbonate of soda. Add to the egg mixture and beat together. Stir in the chocolate chips.
Roll the mixture into 2cm balls and space them well apart on the baking sheets, press each gently with a fork to flatten slightly.
Bake in the oven for 10-12 minutes or until golden. Leave to cool on the sheet for 2 minutes and then transfer to a cooling rack to cool completely.
The cookies can be stored in an airtight container for 2-3 days or up to 1 week in the fridge.
Tip: You can freeze the flattened cookies before baking. Cook from frozen for 12-14 minutes at 190°C