Preheat oven to 400 degrees. Cut chicken breasts in half the long way. Cover with parchment paper and beat the chicken with a meat tenderizer. This will make the meat more tender and better absorb the flavor. If you don't have a meat tenderizer, use an empty wine bottle- it works the same :)
Assemble your dredging station. Put the flour in one bowl, eggs in another bowl, and then put the panko, regular breadcrumbs, and parmesan cheese in the last bowl. Dredge the chicken in the flour, then in the egg, then in the breadcrumb mixture and let sit.
In a saucepan, saute onion and garlic. Once transluscent, add remaining Ragu sauce (leave about 1/4 in the jar). Then add heavy cream and butter and let simmer.
Pour some of the tomato sauce in the bottom of a baking pan, just enough to coat the pan. Put a large dollop of the tomato sauce on top of each chicken breast and then top each breast with a generous amount of mozzarella. Bake in the oven on 400 degrees for 20 mins and then broil for 5-7 mins.
While chicken is baking, make spaghetti according to box instructions. Be sure to lightly salt your water before adding the pasta.
Remove chicken from oven and let sit for 3-5 mins. Then assemble your chicken parmesan and enjoy! :)