Clean and dry the beaters. Add brown sugar and the remaining 2/3 cup granulated sugar to the eggs and yolks and beat with the mixer at medium speed until thick and light in color, about 3 minutes. Scrape down the sides of the bowl with a rubber spatula; beat in the toasted ground nuts and vanilla until combined. Beat in flour, cocoa powder, salt and cinnamon just until combined, scraping down the sides as needed. Fold in 1 cup of the beaten whites with a rubber spatula until smooth, then fold in the remaining whites with very gentle arcs, just until incorporated (some white streaks may still be visible). Gently pour the batter into the prepared pan.