1. Sift together flour, cocoa, baking powder and salt. Melt chocolate over simmering water or gently in the microwave, stirring occasionally, until smooth. Set aside.
2. Beat eggs with a fork to break them up. Add vanilla and sprinkle with coffee powder. Set aside.
3. Beat butter 30 seconds or so until smooth and creamy. Add sugars, beating until well combined. Add eggs and beat until well combined. Add chocolate in a steady stream (or by large spoonsful), removing remains with a scraper. Scrape the sides of the bowl and beat to combine all. Add flour and mix on low speed just until combined—less than a minute. Cover the bowl with plastic wrap and let it stand 30 minutes to set.
4. Heat oven to 350°, arranging racks in the upper and lower middle of the oven. Line 2 cookie sheets with parchment paper. Scoop dough into heaping tablespoons and place 1½ inches apart on parchment.
5. Bake cookies until the edges are set and centers are soft, about 10 minutes, switching their positions front to back and bottom and top at about 5 minutes. Cool on baking sheets 10 minutes, then slide parchment onto cooling racks to cool completely. Use a metal spatula to remove cookies.

Makes about 32 cookies