How to Make It
Make latkes: Put potato and onion in a colander and set in the sink. Let drain, pressing with the back of a spoon occasionally, until no more liquid comes out, at least 30 minutes. Turn potato and onion into a medium bowl and stir in salt, pepper, flour, and egg. Mix well.
Preheat oven to 300°. In a large nonstick frying pan, heat 2 tbsp. oil over medium heat until shimmering. Shape 2 tbsp. potato mixture into a ball and add to pan, flattening slightly with back of a spoon. Shape and flatten 5 more balls the same way and fry until golden brown, about 3 minutes per side. Transfer to a baking sheet and put in oven to keep warm. Repeat with remaining potato mixture, adding more oil to pan as needed.
For gingered yogurt and green apple topping: To same pan used for latkes, add apple, drizzle with vinegar, and toss to coat. Cook until slightly softened, 1 minute. In a serving bowl, mix yogurt with ginger. Spread ginger yogurt on latkes, then top each with a half-slice of apple.
For avocado cream topping: In a food processor, purée avocado, sour cream, salt, pepper, and lemon juice. Dollop avocado cream onto latkes, then top with smoked trout and cilantro leaves.
For salmon roe topping: Spoon sour cream onto latkes, then top with salmon roe and dill sprigs.
Make ahead Latkes, through Step 2, up to 1 day, chilled; reheat in a 350° oven until crisp, about 10 minutes.
PER LATKE WITH GINGERED YOGURT AND GREEN APPLE TOPPING 90 Cal., 59% (53 Cal.) from fat; 1.8 g protein; 6 g fat (0.6 g sat.); 7.2 g carbo (0.5 g fiber); 56 mg sodium; 10 mg chol.
PER LATKE WITH AVOCADO CREAM TOPPING 127 Cal., 61% (78 Cal.) from fat; 4.7 g protein; 8.8 g fat (1.4 g sat.); 7.6 g carbo (1.2 g fiber); 68 mg sodium; 28 mg chol.
PER LATKE WITH SALMON ROE TOPPING 90 Cal., 62% (56 Cal.) from fat; 1.8 g protein; 6.3 g fat (0.7 g sat.); 6.7 g carbo (0.5 g fiber); 57 mg sodium; 20 mg chol.