What I like about a one-dish meal is that it's a wholesome, well-balanced meal.
Leftovers meat, poultry and fish are potentially good to cook one-dish meal with the combination of other greens.
One-dish meal must ideally be simple and easy to cook.
My personal favorite is Kai Choy Fun (Chinese Mustard Green stem/roast pork rice) cooked by my wife.
The ingredients are:
Cooked White rice.
Chinese Mustard Green Stem-cut diagonally (the more the better)
Roast Pork belly-sliced (buy from market)
Shallot-diced and deep fried.
Salt and pepper for taste.