Heat oven to 350°F/177℃.
Line 2 sheet pans with parchment paper. Set aside.
In a medium bowl, whisk together flour, cocoa, salt, and baking powder. Set aside.
In a medium saucepan, combine butter and chocolate.
Melt over low heat, stirring continuously, until smooth. Set aside.
Combine eggs, sugars, and vanilla in the bowl of a stand mixer.
Mix on low for 30 seconds to combine.
Increase speed to high for 10 minutes.
Stir in chocolate mixture.
Add flour mixture.
Mix only to combine.
Immediately drop by scoopfuls onto prepared pans and place in oven.
Bake for 10-12 minutes, or to desired level of doneness.