Microwave both chocolates and butter in a large microwaveable bowl on high 1 1/2-2 minutes or until chocolate is almost melted, stirring halfway through heating time. Stir until chocolate is completely melted and smooth.
Stir sugar into chocolate mixture until blended. Mix in eggs and vanilla.
Stir in flour, baking powder, and salt. Stir in nuts. (Dough will be soft).
Drop by rounded tablespoonfuls, 1 1/2 inches apart, onto ungreased cookie sheet.
Bake 12 minutes or until set. Do not overbake.
Cool 5 minutes; remove from cookie sheet. Cool completely on wire racks. Store in airtight container.