Preheat the oven to 375 degrees.
Dice the ham and onions. Place the ham into a bowl and set aside.
Take some butter and add to a frying pan. Sautee until a light brown then remove them and place them into a bowl.
While cooking the onion combine the flour, garlic powder, and oregano to a plate. Split 3 chicken breasts so that they are now between 6-7 pieces.
To the same pan that the onion was cooked, add the olive oil. Dredge chicken in flour mixture then add to pan. Brown 2-3 minutes on each side. You will not cook these all the way through, this is just to brown the chicken so cook 2-3 minutes per side only.
Add the chicken to a greased dish.
In a bowl put the cream of chicken, milk, garlic powder, dried oregano, and Dijon mustard. Stir to combine completely.
Pour on top of the browned chicken in the prepared dish. Cover with onions and diced ham. DO NOT add cheese at this time.
Cover with tin foil and bake for 30 minutes.
After the dish has baked for 30 minutes take it out of the oven and add the cheese.
Leave the foil off and put back into the oven for an additional 15 minutes. Enjoy!