What's for Dessert? Super Fudgy Brownies

I am still after that elusive "perfect" brownie recipe. These were deliciously moist and fudgy, but not quite what I am looking for. Another search continues...

1 cup (2 sticks) butter
12 oz semisweet chocolate chips, divided
1 cup flour
1 t baking powder
1/4 t salt
1/2 cup each: white and brown sugar
4 eggs
2 t vanilla

Preheat oven to 350°. Spray an 8" square baking dish liberally with cooking spray. Set aside.

Melt butter and chocolate chips in a medium bowl in the microwave, stirring occasionally til mixture is smooth. Set aside to cool slightly.

Mix together flour, baking powder and salt in a medium bowl.

In a large bowl, mix together sugars, eggs, and vanilla. Whisk in cooled chocolate mixture, stirring til blended and smooth. Stir in flour mixture. Fold in remaining chocolate chips.  Pour batter into prepared pan.

Bake til top is set and sides begin to pull away from edges, about 40-45 minutes.

Cool brownies in pan before slicing.