Brown the sausage in a heavy skillet, stirring and breaking up into small pieces.
Spoon out one tbsp of the sausage fat and set aside.
Drain and discard the remaining fat and set aside the browned sausage.
Heat the chicken broth in a small saucepan until boiling.
Adjust the heat to maintain a steady simmer.
Combine the reserved sausage fat and olive oil in a heavy saucepan and heat over low heat.
Add the onion and saute until golden, about 8 minutes.
Add the garlic and saute 1 minute more.
Stir in the rice and saute over low heat, stirring, about 2 mminutes.
Add enough of the hot broth, about 1/2 cup, to just cover the rice.
Adjust the heat to maintain a steady simmer and cook the rice, stirring constantly, until almost all of the broth has been absorbed, about 3-4 minutes.
Add another ladle of broth.
Cook, stirring constantly, until all the broth has been absorbed.
Continue adding the broth, one ladle at a time, cooking and stirring.
Add the next ladleful when the broth is absorbed and the rice begins to pull away from the sides of the pot as it is stirred.
Add the tomatoes, chopped basil and half of the reserved cooked sausage during the last ten minutes of cooking.
Cook until the rice is creamy and firm, but not chalky in the centre when it is tasted.
The total cooking time is 30 minutes or more.
Remove from the heat.
Stir in the butter, cheese and salt.
Briefly reheat the reserved browned sausage.
Spoon the risotto into shallow bowls and divide the warmed sausage evenly among the bowls.