In the bowl of a stand mixer fitted with the paddle attachment (or using a hand held mixer), beat the eggs, sugar, and vanilla until light in color, thick, and ribbons form, about 3 minutes on medium-high speed. Reduce the speed to low and slowly add the melted chocolate and butter. Beat until blended. Add the flour mixture and beat until blended. Fold in the mint chocolate chips. Cover the bowl with plastic wrap and refrigerate until the dough is firm enough to roll into balls, at least 3 hours.