- In a pot over high heat, brown the mushrooms, onion and garlic in the butter. Add the meat and cook, breaking it up with a wooden spoon, until just cooked. Add the tomato paste and cook for 1 more minute, stirring constantly.
- Add the broth and bring to a boil. Simmer for 30 minutes or until the liquid has reduced by half and has thickened slightly. Sprinkle with the parsley. Season with salt and pepper.
- Meanwhile, in a large pot of salted boiling water, cook the spaghetti until al dente. Drain. Transfer the pasta to the meat sauce and toss to coat well. Adjust the seasoning.
- With the rack in the middle position, preheat the oven’s broiler.
- On a baking sheet, place 4 oven-safe bowls. Divide the pasta among the bowls and top with a slice of cheese (see note). Broil for 3 to 4 minutes or until the cheese has melted. Serve with a green salad, if desired.
If you’re not eating right away, you can refrigerate the bowls at this stage. When you’re ready, simply pop them in the oven.