1) Preheat the oven to 350°F. Lightly grease or line with parchment two baking sheets.
2) In a medium bowl, mix together the melted butter, sugar, baking powder, espresso powder, and salt.
3) Add the eggs and vanilla, beating until smooth.
4) Stir in the cocoa powder and flour; the dough will be sticky.
5) Mix in the chocolate chips and chunks.
6) Drop the cookies by tablespoonfuls (about 1 1/2" balls) onto the prepared baking sheets, leaving about 1 1/2" between them. A tablespoon cookie scoop works well here. Cookies will bake into chunky mounds, and you don't need to leave a lot of space between them; they won't spread much.
7) Bake the cookies for 8 to 10 minutes, until they're just set; they'll still be a bit shiny in the center. Remove them from the oven, and allow them to cool on the pan.
Yield: about 3 dozen cookies.