Heat oil in a heavy frying pan to 325 degrees F. Add the plantain quarters in 3 batches and fry until soft, about 2 minutes per side, turning once. Transfer to a paper towel-line plate with a slotted spoon to drain. Repeat with the remaining plantains.

Heat the oil to 375 degrees F. Using a tostone maker, tortilla press, meat pounder or other heavy object, flatten each plantain slice until 1/8 inch thick. Fry the tostones until crisp and golden brown, about 1 minute per side. Drain on paper towels. Sprinkle immediately with salt.

Combine all ingredients in a medium bowl and season with salt and pepper to taste.

Place avocados, chipotle and lime juice in a medium bowl and mash with a fork until almost smooth, but some texture remains. Add the creme fraiche and fold until almost combined (should have a marbled appearance) and season with salt and pepper to taste

Assemble:

Place a heaping tablespoon of salmon tartar in the center of each tostones and top with a teaspoon of avocado-chipotle relish. Garnish with cilantro leaf. Serve immediately.