Prep

1. Cut chicken breast into 2 inch pieces. 
2. In a bowl add chicken, sliced onions and One Heart seasoning. Toss to coat evenly. Cover and refrigerate for one hour.

Assembly and Cook

1. Preheat oven to 350.
2. On a sheet pan arrange flat bread and drizzle with a little olive oil. Add half the cheese and set these aside.
3. In a skillet over medium high with remaining olive oil sauté the marinated chicken and onions. Cook these stirring frequently for 5 minutes to brown both the onions and chicken. 
4. Top the prepared flatbread with chicken and onions, then with chopped mustard greens. Add remaining cheese on top.
5. Bake flatbread pizzas for 15 minutes.