Grate 2 medium russet potatoes and 1 yellow onion into a large bowl. Soak the mixture in salted water for 20-30 minutes to remove excess starch. Once the time is up, drain and thoroughly squeeze out any moisture with a clean kitchen towel.

In a big mixing bowl, combine the grated potatoes and onion with 1 egg, 1/4 cup of matzo meal, 1 teaspoon kosher salt, and 1/2 teaspoon ground black pepper. Stir until everything is well blended and forms a cohesive mixture.

Heat 1/4 inch of vegetable oil in a heavy skillet over medium heat until hot. Scoop 1/4 cup of the latke mixture into the hot oil and flatten gently. Fry until golden brown, about 6-10 minutes, then carefully flip and cook the other side until equally crispy. Keep the cooked latkes warm in a 200°F oven while you finish the rest.

In a separate saucepan, bring water to a gentle simmer and add 1 tablespoon of white vinegar. Crack each large egg into a small bowl, then carefully slide it into the simmering water. Poach the eggs for 4½ to 5 minutes until the whites are set but the yolks remain runny. Remove with a slotted spoon and drain on paper towels.

In a blender, combine 3 egg yolks, 1 tablespoon of fresh lemon juice, and a pinch of salt. Blend on low speed while slowly drizzling in 1/2 cup of melted unsalted butter until the mixture is creamy and thickened.

To serve, place one crispy latke on a plate. Top with a piece of smoked salmon, followed by a poached egg. Drizzle with hollandaise sauce and garnish with chives, flaky salt, and black pepper.