Preheat oven to 350°F/180°C. Lightly grease or line 9x13 baking pan with parchment paper.
In a medium bowl, whisk together flour, cocoa, salt, and baking powder. Set aside.
In a stand mixer fitted with paddle attachment, or you can use a hand mixer, on medium high speed, cream together butter and sugar until light and fluffy, about 2-3 minutes.
Add in eggs, one a time, and beat until thoroughly combined. Beat in vanilla, and food coloring until combined.
Add the flour mixture until a soft dough forms. With a wooden spoon, or spatula, stir in the white chocolate chips to combine.
Press the cookie dough into the bottom of the prepared pan into an even layer.
Bake for about 20 minutes until the edges start to pull away from the sides and a toothpick entered into the center comes out clean Remove from the oven and allow to completely cool in pan before frosting.