Cut the potatoes and sweet potatoes into 2-cm wide slices, without peeling them. Cook them in a pot with water and salt, and once they come to a boil, remove from the heat and strain.
Sauté in a pan with oil until brown on each side, and set aside.
Mash the avocado and season. Set aside.
Sauté the shrimp until brown in a hot pan with olive oil and garlic.
To assemble, put a tablespoon of avocado on top of the potato and sweet potato slices, then a shrimp, and finish with a blueberry.
Optional: sprinkle with some minced coriander for more flavor.