Prep mise en place: Wash and spin dry the mixed greens so the dressing will cling evenly (water dilutes the vinaigrette). Peel and pit the avocado; slice in half then score the flesh into 1/2-inch cubes before scooping out so you keep tidy pieces. Thinly slice 1/4 red onion into half-moons and place in a small bowl with a pinch of salt to mellow the sharpness while you finish the other prep.

Segment the orange (supremé): With a sharp knife, trim the top and bottom of the orange so it sits flat. Slice away the peel and pith following the curve of the fruit. Working over a bowl to catch juices, cut between the membranes to release segments. Save any juice for the vinaigrette — using the fruit's juice brightens and ties the salad together. Segmenting gives clean bites and prevents chewy membrane pieces.

Make the citrus vinaigrette: In a small bowl or jar combine 2 tbsp extra-virgin olive oil, 1 tbsp fresh orange juice (from the reserved juice), 1 tbsp lemon juice, 1 tsp Dijon mustard, 1 tsp honey, and a small minced garlic clove if using. Whisk (or shake) vigorously to emulsify. Taste and adjust salt and pepper. Emulsifying (whisking oil into the acids + mustard) creates a silky dressing that coats the greens and avocado without separating.

Warm the shrimp (optional but recommended for extra flavor): Heat 1 tsp olive oil in a nonstick skillet over medium-high. Add the peeled cooked shrimp in a single layer and sear for 30–60 seconds per side just to warm and develop a touch of color — this adds aroma and a slightly caramelized flavor. Do not overcook: these shrimp are already cooked and will turn rubbery if heated too long.

Assemble the salad: In a large bowl, lightly toss the mixed greens with about 2 tablespoons of the vinaigrette to coat; you can always add more at the table. Distribute the dressed greens between two plates. Arrange avocado cubes, orange segments and warmed (or chilled) shrimp on top in an attractive pattern. Scatter the drained red onion slices over the salad and finish with a drizzle of any remaining vinaigrette, a pinch of flaky sea salt and freshly ground black pepper.

Final season and serve: If you like, add a small drizzle (1/2 tsp) of good extra-virgin olive oil or a few drops of high-quality sherry vinegar for depth. Serve immediately so the avocado stays fresh and the greens remain crisp. The contrast of warm shrimp and cool fruit/greens is especially appealing.