In a mixing bowl, beat together butter and sugar until creamy.
Over hot water, in a heat proof glass bowl (or double boiler) melt 1 cup of mint-flavored chocolate morsels stirring until smooth. *Be very careful not to burn yourself.
Add melted morsels and vanilla extract to the butter mixture and stir until combined. Mix in eggs.
Then add in the flour, baking powder, and salt. Mix until combined. Then stir in the remaining mint-flavored chocolate morsels.
Wrap dough in plastic wrap and refrigerate for at least 4 hours or overnight.
Preheat oven to 350 degrees F.
Using a cookie scoop, shape the dough into balls and roll/coat in powdered sugar.
Place cookies on a parchment-lined baking sheet and bake for 10-12 minutes.
Let the cookies cool for 5 minutes on the cookie sheet before cooling completely on a cooling rack.