Preheat oven to 350°F. Melt semisweet and bittersweet chocolates with butter over low heat, stirring occasionally until smooth. Cool.
In a separate bowl, sift together flour, baking powder, and salt. In another mixing bowl, beat eggs, sugar, and vanilla until fluffy. Add melted chocolate and then flour mixture. Beat until blended. Stir in chips and nuts.
Drop by the tablespoonful onto lightly greased or parchment-lined baking sheets. Bake 10 to 12 minutes, or until tops of cookies are uniform in color and no longer look wet. When done, they should come off of the baking sheet easily. Cool on racks.