Combine 8 ounces of chocolate with the butter in a large stainless steel bowl or double boiler over simmering water. Stir frequently until melted and smooth. Remove from heat and set aside. Continue to heat the simmering water.
Meanwhile, whisk flour, baking powder, and salt together in a small bowl. Set aside.
In another large heat-proof bowl, whisk eggs, sugar, and vanilla together. Set the bowl over the simmering water and stir constantly until the mixture is just warm to the touch. Stir the egg mixture into the warm (not hot) chocolate. Stir in the flour mixture, and then add the pine nuts (if using) and chocolate chips.
Drop slightly rounded tablespoons of batter 1 1/2 inches apart on parchment-lined baking sheets. Bake in an oven preheated to 350° F until the surface of the cookies looks glossy and set but the centers are still gooey, about 12 minutes. Place baking sheets on racks and cool completely.