1. Heat oven to 325 F. Line 2 baking sheets with parchment. In a bowl stir together 1/3 cup flour, baking powder, and salt; set aside.
2. In a heatproof bowl set over a pan of simmering water melt the butter, 1 cup chocolate chips, and the unsweetened chocolate, stirring occasionally. Remove from heat and set aside to cool.
3. Using an electric mixer, beat the eggs, espresso powder, and vanilla until combined. Add the sugar and beat until light and thickened, about 2 min. With the mixer on low speed, slowly add the melted chocolate. By hand, fold the flour mixture into the batter. Fold nuts into the batter with remaining chocolate and peanut butter chips. Drop 1/2 cup mounds of batter onto the prepared baking sheets. Press mounds to flatten slightly. Bake until set around the edges and slightly gooey in the centers, 18 min. Allow cookies to cool on baking sheet. Store in an airtight container for up to 3 days.