Heat the olive oil in a non-stick pan until hot. Fry the shrimp for 2-3 minutes on each side until opaque and cooked through. Set aside to reach room temperature.
Wash and dry the lettuce leaves then arrange them on a plate or salad bowl to make a bed for the salad.
Add the mayonnaise and Dijon mustard to a bowl and mix. Add the cooked shrimp and gently mix until well-coated. Season to taste with salt and freshly ground black pepper.
Transfer the shrimp salad on top of the lettuce leaves and garnish with chopped green onions.