Drain beans. Stir in tomato paste, tomatoes, coffee, beans, and stock. Bring to a boil, then reduce heat to low; simmer 30 minutes (or 1 hour). Break chocolate into pieces; stir in during last 5 ...
The leftover aspect of this is twofold: first, don’t discard the bits and pieces of pasta at the bottom of a packet, and second, don’t chuck out that leftover cooked pasta.