Adjust oven racks so that one is positioned in the upper middle region and the other is in the lower middle area. Preheat oven to 300 degrees F.
Line 2 or 3 rimmed baking sheets with parchment paper.
Sift flour, baking powder, baking soda, salt, and cocoa powder into a small bowl. Stir with a fork or whisk to mix.
Combine the 6 ounces of chopped bittersweet chocolate with 3 tablespoons of oil and the butter in a medium glass bowl. Microwave at 50% power for 3 minutes, stirring after each one minute interval. After the last minute, you will still see a few lumps of chocolate, but stir for about 60 seconds, and they will melt. Whisk the milk into the chocolate mixture until it is completely incorporated. Allow to sit while you beat the eggs and sugar.
Using a hand mixer, beat the eggs and slowly add the sugar. Beat for about 4 minutes, until the mixture is very thick and pale yellow.
Add the melted chocolate mixture to the egg mixture, whisking to combine.
When there are no more streaks in the chocolate mixture, fold in the flour mixture using a rubber spatula. Continue to fold, scrape the sides, and turn over in the bowl until no dry ingredients are visible. Fold in the chocolate chips, distributing evenly.
Scoop heaping tablespoons of batter (a 1-tablespoon scoop that has been greased with Pam works well) and place 12 on each cookie sheet. (My batch made 29, so I had to use a third cookie sheet.) The mounds of dough should be spaced about 2 inches apart. Moisten fingertips and pat to make roundish balls; they don’t need to be perfect.
Place two cookie sheets on the two shelves in the oven, bake for 8 minutes, then rotate the pans and switch their oven shelves. Bake an additional 8 minutes (Total baking time is 16 minutes). The cookies will look like they’re soft and raw between the cracks on their tops, but they will continue cooking once out of the oven.
If you have a third pan, bake those cookies now.
Leave the cookies on the parchment-lined pans on a rack for 30 minutes before transferring to a cooling rack individually.