Cook and dice chicken, if needed. (No cooking time if already cooked.*)
Zest and juice one orange and place the juice and zest into a small bowl. Add rice vinegar, olive oil, dried mustard, and honey. Use a whisk to blend. Set aside.
Peel the other orange. Separate the segments, then slice each segment into 4 pieces.
Add oranges pieces, spinach, cooked and diced chicken and onions to a large bowl and toss.
Divide the salads between serving dishes. Pour dressing over the top and sprinkle with almonds.
Serve Orange Spinach Chicken Salad with Orange Mustard Vinaigrette.