Preheat the oven to 190ºc/170ºc fan and line a 9x9inch square tin with parchment paper, and leave to the side for now.
Add the butter to a bowl, and add in the two sugars. Mix until combined.
Add the eggs and vanilla and mix again.
Add the flour, cornflour, bicarbonate of soda and salt and mix again.
Add the chocolate chips and most of the mini eggs and mix into the cookie dough.
Press the mixture into the bottom of the tin and press in the handful of mini eggs into the top for decoration.
Bake the traybake in the oven for 18-22 minutes, until the top of the cookie bake looks ‘dry’!
Leave the cookie bars to cool, and then portion and enjoy!
