To make the pesto, add basil, roasted garlic, toasted pecans, lemon juice, olive oil, salt and pepper to a food processor and blitz until well combined. Set aside.
Add Italian sausage to a pan over medium high heat and cook until crumbly, about ten minutes.
To a large pot of salted water add spaghetti and cook for eight to nine minutes, drain and reserve 1/2 cup cooking water. Return the pasta to the pot, add the pesto, Italian sausage and chilli flakes. Mix to combine. Add a little bit of the cooking liquid to create a sauce.
Divide pasta into bowls, top with a few slices of buffalo mozzarella. Enjoy!