Preheat your oven to 180°C (160°C for fan ovens) and line a large tray or two with baking paper.
In a large bowl, whisk the butter, caster sugar and brown sugar together until smooth.
Add the egg and the vanilla extract and mix well.
Add in all of the self-raising flour and mix it in. When it starts to stick together, use your hands to press the mixture into a ball of dough.
Add the crushed Mini Eggs and chocolate chips then gently knead them into the dough with your hands.
Divide the dough into 12 equal-sized pieces and roll into balls.
Place the dough balls on your lined trays, making sure to leave a couple of inches between each cookie to allow space for spreading.
Bake the cookies for 11-12 minutes, until they're just turning golden at the edges.
While the cookies are still warm, stick extra Mini Eggs on top using the melted chocolate.
Wait until the cookies are cool and the melted chocolate has set before you remove them from the tray.