Preheat oven to 400°.
Rinse salmon and cut into 4 equal pieces. Place in an 8- or 9-inch square pan. Sprinkle with rosemary and lemon peel, then drizzle with 1 tablespoon olive oil and pisco. Cover and chill at least 2 hours or up to 1 day; turn fish over occasionally.
Meanwhile, pour about 1 teaspoon olive oil into your palm, then rub chiles and onion wedges with oil. Spread vegetables out in a 10- by 15-inch baking pan.
Bake until chiles have black spots and onions are tinged with brown, 25 to 30 minutes; turn occasionally. Let cool 15 minutes, then remove chile skins; pull out stems and discard seeds. Cut chiles into 1 1/2-inch-wide strips.
Shape mashed potatoes into 4 equal patties (tortas de papas). Rub a 12-inch nonstick frying pan lightly with olive oil. Set pan on medium-high heat; when hot, lay patties in pan; brown on each side, turning once using a small spatula to push patty onto wide spatula, about 8 minutes total. Transfer to a baking sheet or pan; keep warm in a 400° oven up to 20 minutes.
While potato patties brown, put salmon, uncovered, in the same 400° oven and bake until the pink color of fish is even to the center (cut to test), 15 to 18 minutes; baste several times with pan juices.
Place a torta de papa on each plate, set a piece of salmon on top, and surround with onions and chiles. Then top each portion equally with lettuce, queso fresco, crema fresca, and avocado. Add salt and pepper to taste.
Wine pairing: Sparkling brut Champagne with a high percentage of Pinot Noir, such as Korbel Natural Sonoma County Champagne, Russian River Valley.
Servings Makes 4 servings
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.