Pre heat your oven to 200c.
Get your frying pan on a medium heat and add some oil to coat the bottom generously. Coat the chicken (one piece at a time) in the seasoned flour, egg and then breadcrumbs. Place each chicken in the heated oil and flip when golden.
For the marinara sauce heat a saucepan over medium heat, adding a little oil, and fry the onions and garlic. Add the rest of the ingredients for the sauce, cook and reduce a little, and taste for seasoning.
Add the marinara sauce to the bottom of an oven safe dish, and place your chicken on top of the sauce, top with more marinara sauce and grated mozzarella.
Bake for 30 minutes or until cheese is golden, in that time get your spaghetti cooked in seasoned boiling water. Once cooked serve with the chicken.