Melt the butter over medium low heat in a small sauce pan. Let cool to room temperature.
Meanwhile, sift or mix together flour, cocoa powder, salt, baking soda and baking powder in a medium bowl.
In a small measuring cup, add the eggs, milk and vanilla extract, whisk together. Set aside.
Add the cool butter and sugar in a stand mixer mixing bowl and beat with a paddle attachment on medium speed until fluffy and lighten in color, about 2 minutes.
Add the egg mixture to the butter/sugar mixture and beat another 2 minutes.
Lower the mixer speed and gradually add the flour mixture, scraping the side and bottom of the bowl as necessary.
Once all the flour is incorporated, turn the mixer speed to stir and add the butterscotch chips, mix until the chips are evenly distributed.
Use a large ice cream scoop (about 2 ounces in size) to portion cookie dough onto a parchment paper lined baking sheet or large container. Cover and refrigerate for at least 1 hour.
Preheat oven to 350°F.
Place already portioned cookie dough onto a parchment paper lined baking sheet, spacing 1” - 2” apart.
Bake for 15 minutes, in multiple batches, in the middle of the oven.
Let cool on the baking sheet for 5 minutes then transfer with a spatula to cool on a wire rack.