Put the mini eggs in a large freezer bag, seal, and break into large pieces with a rolling pin. In a small bowl, whisk together flour and salt.
In a stand mixer (or with a handheld) cream butter and sugar on medium speed until light and fluffy.
Slowly add flour + salt mix to the bowl with the creamed butter and sugar and stir until just until fully combined. Add the mini egg pieces, and stir until fully incorporated.
Cover the bowl and chill in the fridge for 30 minutes to overnight. The longer you can chill them the better, as they will hold their shape and sink less.
Preheat the oven to 350 degrees. Prepare 2 baking sheets with parchment paper. Shape out about 15 cookies per sheet - about 2 tablespoons per cookie with 2 inches between each cookie. Gently flatten the top (they will only sink slightly).
Bake, one sheet at a time, for 20-25 minutes, until just golden brown. Cool on a baking rack.