Preheat the oven to 350 degrees. Use convection bake if you have it.
Using a stand mixer fitted with the paddle attachment or a hand mixer, cream the butter and brown sugar on high for 1 minute. Scrape down the bowl once complete.
Add in milk, egg and vanilla extract. Mix until combined. Scrape down the bowl once complete.
In separate bowl, whisk dry ingredients together (flour, baking soda, salt).
Add dry ingredients to wet ingredients in 3-4 portions. Mix until combined
Using a wooden spoon or strong silicone spatula, mix in the chocolate chips and crushed Cadbury mini eggs. You can also use a mixer to do this part.
Grease and line a 9" round cake pan or an 8x8 pan with parchment paper.
Spread half of the dough evenly throughout the pan using a greased spatula or your fingers.
Evenly place 8 Reese's eggs across the dough (add more if there is extra space!)
Use the rest of the dough to evenly cover the rest of the pan.
Sprinkle Cadbury Mini Eggs evenly over the top of the dough (not crushed).
Bake for 20-25 minutes or until the top of the cookie bars are light brown.
Let the bars cool to room temperature before slicing & serving.
