I started out whipping 3 sticks of unsalted butter (softened) with 2 cups of packed dark brown sugar in my standing mixer. While that is going, in a separate bowl I mixed 3 1/4 c. all-purpose flour, 1 c. cake flour, 1/2 tsp. baking powder, and 1/2 tsp. baking soda.
Back to the standing mixer. Once the butter/brown sugar is whipped, I then added 1 tbsp. vanilla extract and 2 eggs and beat this again on medium speed until incorporated. I then added my flour mixture to the bowl and mixed it on low until all incorporated (this is a very thick cookie dough). While this is going, I took 3 c. dark chocolate chips (60% cacao) and melted it in a ceramic bowl in the microwave, heating it for 1 minute and then stirring with a wooden spoon until all is melted (you have to be careful melting chocolate in the microwave; it can burn easily). I then added this to the mixer and beat on low until all incorporated.
Then I removed my mixing bowl from the mixer and added 1 1/2 cups of semi-sweet chocolate chips to the cookie dough and folded it in. I used an ice cream scooper to get perfectly-round and perfectly-sized cookies. One trick I use is I put some chocolate chips in a small bowl on the side and after forming each cookie, place a chip or three on the top of each cookie before placing it on the cookie sheet so it looks like it has even chip distribution. I then baked the cookies in the oven for 12 minutes at 375 degrees. The cookies come out dense, chewy, and chocolaty. My chocolate-loving hosts are always pleased.