Pre-heat your oven to 180C Fan/200C/400F/Gas Mark 6, line your baking tray(s) with baking paper
Either using a stand mixer with the paddle attachment, or with a wooden spoon, mix the butter and both sugars together until fluffy and paler in colour. This will take 3-5 minutes in an electric mixer
Add the egg and vanilla extract and mix in
Add the plain flour, baking powder, bicarbonate of soda and salt and mix them in
Finally, stir in the crushed Mini Eggs until evenly distributed
Divide the dough into 16 portions, I weighed the dough and used 50g per cookie
Roll into balls using your hands, don't flatten them out at all, the taller they are the less they will spread. Push three Mini Eggs into the top of each cookie dough ball
Bake for 12 minutes, remove from the oven and gently push a few more Mini Eggs into the top of each cookie
Leave to cool for at least 10 minutes on the baking trays before moving to a cooling rack
Store leftovers in an airtight container and eat within 3 days