How to Make It
In a small bowl, whisk together the vinegar and mustard. Slowly whisk in the olive oil. Season with salt and pepper.
In a small saucepan of boiling water, cook the shrimp until just opaque, about 1 minute. Drain.
Set the avocado halves on plates. Spoon the shrimp into the avocado halves and drizzle with the dressing. Garnish with the tomato and chives.