1. Warm the butter and olive oil in a medium-size Dutch oven or heavy-bottomed sauce pot placed over medium heat. When the butter has melted, add the onions and pancetta, stirring to coat them thoroughly. Sauté for 5 minutes, reducing the heat to medium-low if necessary to prevent the onion from burning. Sprinkle in the marjoram and a generous grinding of black pepper and continue to sauté for another 5 minutes, or until the onion is translucent and the pancetta has just begun to crisp but is still mostly tender.

2. Pour in 6 cups of chicken broth and raise the heat to medium-high. Toss in the parmesan rind if you are using it. Bring the broth to a boil. Stir in the pasta and peas -- use 1 1/2 cups of pasta for a soupier soup and 1 3/4 cups for a thicker soup. Allow the broth to return to a boil and boil for about 8 minutes, or until the pasta is al dente (the exact cooking time will depend on the brand and shape of the pasta). Add an additional splash of broth if the soup seems too thick.

3. Remove the soup from the heat and stir in 1/2 cup of grated parmesan. Taste and add salt and additional pepper if you like. Divide the soup between 4 individual bowls and sprinkle additional cheese over each serving. Serve immediately.