Boil the shrimp in a pot of boiling water until tender for approximately 2-3 minutes.

Drain the shrimp and rinse them under cold water to stop the cooking process. Drain well and towel dry.

In a small bowl, combine the mayonnaise and ketchup. Mix until well blended.

Carefully cut the avocado lengthwise around the pit, remove the pit, and cube the flesh without cutting through the skin.

Place the avocado cubes in a medium bowl, add the cooled drained shrimp and the mayonnaise mixture, and gently combine.

Season the mixture with salt and black pepper to taste, mixing lightly to incorporate.

Spoon the shrimp mixture into the empty avocado shells, filling them generously.

Garnish with finely chopped fresh parsley before serving.