Heat the oven to 425°F (220°C) with a rack in the middle. Bring a large pot of salted water to the boil.
Cook the ziti for about 7 minutes — a full 2 minutes short of al dente. It should still have a firm, chalky core. It finishes cooking in the oven, and pasta boiled to done here comes out of the oven soft. Drain and leave it in the pot.
Brown the sausage in a large sauté pan over medium-high heat, breaking it up as it cooks, for 5 to 6 minutes. Chicken sausage is lean and will want to stick, so let it sit undisturbed for the first couple of minutes and it will release on its own. Lift it out with a slotted spoon and set aside.
Add the tablespoon of olive oil to the pan. Chicken sausage renders very little, so there is nothing to pour off here - you are putting fat back in rather than taking it out. Lower the heat and cook the garlic for 1 minute until fragrant but not coloured.
Add the crushed tomatoes, salt, sugar and red pepper flakes. Simmer uncovered for 10 minutes, stirring now and then, until it thickens slightly.
Take the pan off the heat and stir in the cream, 1/3 cup of the Pecorino, the browned sausage and the basil. The sauce should turn a warm brick-orange. This cream is doing the job ricotta usually does, except it goes everywhere instead of sitting in pockets.