Preheat the oven to 350°.
Cream butter and sugar together. Beat in eggs one at a time. Add vanilla.
Stir flour, cornstarch, salt and baking soda together in a separate bowl. Add crushed mini eggs. Pour into wet ingredients and mix until combined.
Drop by spoonfuls onto a lined baking sheet.
Bake for 10-12 minutes, don't overbake! I like to take cookies out when the centers still look slightly undercooked. They firm up while cooling.