Just dump everything together, after sauteeing the vegetables.
The mixing gets a bit difficult once you add the spaghetti. I even broke my wooden spatula trying to mix this...so I changed to a stronger hard plastic spatula.
But actually, what works the best is two forks...
This recipe makes a lot. One casserole was for lunch, and the other went into the freezer. I sprinkled red pepper on my casserole to bump up the spice a little. On the one headed for the freezer, I used paprika on the top, because I had plans to serve that when my grandaughters came to visit. Today, I was happy to be able to pull this out of the freezer after breakfast, then put it in the oven for an hour (still icy) to cook at lunch time with Carissa, Lillian and Evelyn here at my house. I think this chicken spaghetti is even better on the second day, so I know we will enjoy it tomorrow too. And the girls really ate this up! This is a great kid pleasing meal that grown-ups love just as much.