Grate 2 large russet potatoes and 1 yellow onion into a bowl. Soak the mixture in salted water for 20-30 minutes. Drain and squeeze out excess moisture.

In a mixing bowl, combine the drained mixture with 1 beaten egg, 2 tablespoons of matzo meal, kosher salt, and black pepper. Mix until well combined.

Heat ½ inch of vegetable oil in a skillet. Drop tablespoons of the latke mixture into the oil, flattening them. Fry for 6-10 minutes per side until golden brown.

In a pot, bring water to a simmer and add a splash of white vinegar. Poach 2-4 eggs for 4½ to 5 minutes. Remove with a slotted spoon.

In a heatproof bowl, whisk 2 egg yolks and lemon juice until thickened. Gradually add melted butter while whisking until emulsified.

Assemble the dish: place a latke on a plate, top with smoked salmon or spinach, a poached egg, and drizzle with hollandaise. Garnish with chives and red onion.