Line your baking sheets with parchment paper.
Cream the butter and sugars together in a large bowl until light and fluffy.
½ cup/125g butter, ¾ cup/150g dark brown sugar, ½ cup/100g white granulated sugar
Add the egg, egg yolk, milk, vanilla, and cake batter flavor to the butter mixture and mix until well combined.
1 medium/large egg + 1 egg yolk, 1 tbsp milk, 1 tsp vanilla
In a separate bowl, whisk together the all-purpose flour, cake flour, baking powder, cornstarch, and salt.
1 and 2/3 cups/200g all-purpose flour, ¾ cup/100g cake flour, 1.5 tsp baking powder, 1.5 tsp cornstarch, ½ tsp salt
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the chocolate chips and chopped mini eggs.
1 cup chocolate chips, 2 cups mini eggs, ½ cup mini eggs
Scoop out the dough using a cookie scoop or spoon and nd weigh it on the kitchen scale, if using, then place them on the prepared baking sheets. For NYC style cookies, make larger dough balls, about 5.5 oz each.
Refrigerate the dough balls overnight or for at least an hour to prevent spreading. I recommend overnight to really allow the flavours to meld together and prevent any spreading.
When ready to bake, preheat your oven to 350°F (175°C) and bake for 12 minutes or until the edges are set and the centers are still slightly soft. Let the cookies cool on the baking sheets for a few minutes before transferring to a wire rack to cool completely.