Tostones w/ Salmon Tartar & Avocado-Chipotle Relish

3 green plantains, quartered crosswise and peeled

3 cups peanut or canola oil

Kosher salt

Cilantro leaves

Salmon Tartar:

1 lb salmon, cut into 1/4" thick dice

2 tablespoons Dijon mustard

1/4 cup capers, drained

1/4 cup finely chopped scallions

3 tablespoons olive oil

2 tablespoons finely chopped cilantro

Salt and freshly ground pepper

Avocado-Chipotle Relish:

2 Haas avocados, peeled and pitted

1 tablespoon pureed canned chipotles

2 tablespoons fresh lime juice

3 tablespoons creme fraiche

Salt and pepper to taste