Preheat oven to 350 F.
Mix together in a small mixing bowl: flour, salt, cocoa, and baking powder.
In a separate microwaveable bowl, melt together butter and ½ cup chocolate chips. Melt at 20 seconds on high, then stir. Repeat until all the butter and chocolate chips are melted.
In a separate large mixing bowl, whisk eggs, vanilla and sugar until well combined.
Slowly pour the melted chocolate mixture into the egg mixture, while stirring.
Add the dry mixture from step 2 and stir until well combined.
Pour into a greased 8 x 8 pan, and sprinkle with remaining chocolate chips.
Bake for 35-40 minutes or until a toothpick comes out clean from the center.