Preheat the oven to 350°F and line 2 x-large or 4 regular baking sheets with parchment.
Sift together the flour, cocoa, baking soda and salt. Set aside.
Using an electric mixer, cream together the butter, both sugars and vanilla. Beat together until light and fluffy, around 3 minutes.
Add the eggs one at a time, beating well after each addition.
Lower the speed of the mixer and add the sifted dry ingredients gradually, mixing well after each addition. Continue until all the batter comes together. The batter will be stiff.
By hand, mix in the 1 1/2 cup dark chocolate-mint morsels.
Use a Tbsp or a small ice cream scoop to evenly divide the batter on the cookie sheets placing 2 inches apart. Divide and press the remaining chips on top of the dough rounds.
Bake for 10 minutes. Remove from the oven and cool on the pan for 5 minutes.
Remove to a cooling rack to cool completely.