Line a baking tray with parchment paper and set it aside.
In a large mixing bowl, cream together butter and sugars until smooth and paler. Add in vanilla and mix through. Tip in the chocolate chips and about 100g of the chopped mini eggs and stir in.
120 g (½ cup + 1 tbsp) unsalted butter, at room temperature, 100 g (½ cup) soft brown sugar, 50 g (¼ cup) caster sugar, 1 tsp vanilla, 100 g (½ cup + 1 tbsp) chocolate chips (I used dark), 150 g mini eggs, roughly chopped
Sift the flour, cornflour, baking powder, bicarbonate of soda (baking soda) and salt into the mixing bowl. Beat it all together until the mixture is evenly combined. Finally, pour in the beaten egg and mix it all together until just combined and starting to form large clumps of cookie dough.
215 g (1¼ cups + 1 tbsp) plain (all purpose) flour, 2 tsp cornflour (cornstarch), 0.5 tsp baking powder, 0.5 tsp bicarbonate of soda (baking soda), 0.5 tsp salt, 1 large egg, beaten
Divide the mixture into 8 equal parts, or if you prefer to weigh it, each part should weigh around 90-95g. Gently squeeze each part of the mixture together into cookie balls, then place them on the prepared baking tray. Using the additional mini eggs set aside earlier, stud each cookie ball randomly all over. Pop the baking tray in the freezer for at least 30 minutes for the dough to firm up.
150 g mini eggs, roughly chopped