Cook spaghetti and reserve some pasta water.
Season chicken and sear in butter and oil until golden and cooked through. Remove and set aside.
In the same pan, melt butter and sauté garlic.
Add cream and milk, simmer gently.
Stir in cornstarch mixture, then add cheeses until melted.
Toss spaghetti in sauce with a splash of pasta water.
Serve with chicken on top and garnish with parsley.
