Add enough oil to a very large, deep saute pan to coat the bottom with a thin film and place over medium high heat. When the oil shimmers, add the onion, carrots and celery and saute, stirring to coat with oil, until glassy and just tender, about 5 minutes. Season lightly as they cook. (If the pan does not have much room for the meat, pour vegetables into a bowl near the stove, and return the pan to the heat; otherwise, leave them in the pan.) Add the sausage and beef to the pan, breaking it into walnut-size pieces. Brown the meat well, adjusting the heat so the meat does not stew.
Pour in the wine and keep at a rapid simmer until the pan is almost dry. Then pour in 1 1/ 2 cups beef bouillon and lower the heat to medium. Simmer gently, uncovered, until the bouillon is nearly gone. Stir now and then. Meanwhile, chop the rehydrated porcini into small pieces, reserving the mushroom broth, and bring a large pot of salted water to a boil.
Stir enough mushroom broth into the simmering sauce to cover the meat halfway (about 1 cup), along with the chopped porcini, and continue simmering another 10 minutes. The sauce should be quite loose, but not soupy. Taste and adjust seasoning. It should be highly seasoned. When you think it’s the right consistency, pour over the cream and fold to mix, then shut off the heat and cover.
When the pasta water is at a full boil, add the rigatoni and cook until still firm, but not hard, in the center. When the pasta is almost done, scoop out 1 cup of pasta water and keep it near the stove. Drain the pasta and add it back to the pot. Pour the pasta sauce on top and fold it in with a wooden spoon. The pasta should not be dry. Add a little pasta water or mushroom broth to loosen it. (It will continue to soak up sauce on the way to the table.) Present the pasta on a deep platter or in a tureen. Pass the cheese at the table.
Before starting Food52 with Merrill, I was a food writer and editor at the New York Times. I've written several books, including "Cooking for Mr. Latte" and "The Essential New York Times Cookbook." I played myself in "Julie & Julia" -- hope you didn't blink, or you may have missed the scene! I live in Brooklyn with my husband, Tad, and twins, Walker and Addison.