2 tablespoons olive oil
1 pound 80- to 90%-lean ground sirloin
2 medium thin-skinned white or Yukon Gold potatoes, cut into 1/4-inch cubes
Salt and pepper
2 ribs celery
1 cubanelle pepper
4 cloves garlic
1 quart beef stock
1 14.5-ounce can diced tomatoes
1 herb bundle of 1 fresh bay leaf and a few sprigs each parsley and thyme, tied together with kitchen twine
1 piece Parmigiano-Reggiano rind
1/3 pound (a couple of small handfuls) thin green beans (haricots verts), cut on an angle into 1-inch pieces
Grated Parm, for passing
In a soup pot with a lid, heat the oil, two turns of the pan, over medium-high to high. Add the beef and cook, stirring occasionally and breaking up with a spoon, until browned, about 6 minutes. Stir in the potatoes; season with salt and pepper.
Finely chop the celery, pepper, onion, and garlic and add to the pot. Add the stock, tomatoes, herb bundle and cheese rind; partially cover and bring to a boil over high. Reduce the heat to medium and keep the soup at a low boil until the flavors from the cheese rind and herbs are released, about 10 minutes. Add the green beans and cook until crisp-tender, about 5 minutes more.
Discard the cheese rind and herb bundle. Serve the soup in shallow bowls, passing grated cheese at the table.