Preparation / Directions:
Cut the fish fillets into 3/4" cubes. Poach the fish in the white wine along with the onion slices for about 8 minutes. Let them cool in the liquid, then strain it off.
Peel the oranges and slice thinly crosswise. Remove the seeds. For grapefruit, peel and section, then cut the sections into 2 or 3 pieces. Peel the avocados and cut into cubes. Toss the avocado in a bit of the grapefruit juice.
To make the dressing, blend the oil, juice, and mustard. Salt and pepper to taste.
To serve the salad family-style, toss the ingredients with the dressing and serve. For a fancier presentation, line the bottom of a salad plate with overlapping slices of orange, surround it with avocado cubes and pile the fish cubes in the center. Drape the onions over the fish and drizzle with the salad dressing.