In a medium bowl whisk together flour, cornstarch, baking soda and salt. Set aside.

In the bowl of your stand mixer fitted with the paddle attachment, beat the butter on medium speed for one minute until creamy. Add brown and white sugar and beat on medium speed for about 2-4 minutes, until light and fluffy. Beat in the egg and vanilla extract. Add flour mixture and mix just until combined. Do not overmix. Fold in Mini Eggs.

Place plastic wrap over the bowl and refrigerate for at least 1 hour.

Preheat oven to 350F degrees. Line cookie sheets with parchment paper and remove cookie dough from the fridge.

Scoop rounded balls of dough onto prepared cookie sheet, about 1.5 tablespoons for each. Bake for about 8-10 minutes, until cookies just begin to brown at the edges, but the center is still soft. Leave to cool for 10 minutes or until the cookies are easy to transfer without breaking. Then gently transfer to a wire rack to cool completely.

Store cookies at room temperature in an airtight container for up to 3 days.