Preheat oven to 350º F. Line rimmed baking sheets with parchment paper or silicon baking mats.
Add semisweet chocolate chips and 2 tablespoons butter to saucepan over medium-low heat. Melt the chocolate and the butter together, stirring frequently until smooth and completely melted. Remove from heat and allow to cool completely, about 8-10 minutes.
Whisk together flour, baking powder, salt and cocoa powder in a large bowl. Set aside.
Fit stand mixer with paddle attachment. Add granulated sugar and butter to the bowl of the mixer and beat together until light and fluffy, about 3 minutes. Add in eggs, one at a time, creaming together after each addition. Add in vanilla, making sure it is well combined.
Once all eggs and vanilla have been combined. Turn mixer speed up to medium high speed and beat until pale, light, and fluffy, about 7-10 minutes. Turn down speed of mixer and slowly stir in cooled and melted chocolate. Stir dry mixture until combined, then stir in milk chocolate chips.
Drop tablespoon scoops of cookie dough batter onto lined baking sheets, leaving about 3 inches between cookies to allow them to spread.
Place in preheated oven and bake 12-15 minutes. Remove from the oven and allow to cool completely before removing from the baking sheet. The cookies are fragile while warm, so allow to cool completely before moving.
Triple Chocolate Cookies Recipe https://addapinch.com/triple-chocolate-cookies-recipe/