Step 1Heat the oven to 350 degrees. Place the bittersweet chocolate and butter in a pie pan or other small pan in the oven until the chocolate is just soft enough to melt when you mix it around with a spoon, about 2 to 3 minutes. Cool.
Step 2Using an electric mixer, beat together the eggs and sugar on medium speed until light and fluffy, about 1 minute. Slowly add the cooled chocolate-butter mixture and mix well.
Step 3Add the flour, baking powder and salt, and mix on low speed until well combined. Remove the bowl from the mixer, add the chocolate chips and stir in by hand. Set aside in the refrigerator until the dough is firm, about 20 minutes.
Step 4Using a small scoop, place tablespoons of the dough on a well-greased or parchment-lined cookie sheet. Bake until the cookies are almost set in the center, 11 to 12 minutes.