01 -
Grate the peeled russet potatoes and half a yellow onion. Place in a clean kitchen towel and squeeze out as much liquid as possible from the mixture.
02 -
In a large bowl, combine the grated potatoes and onion with the beaten egg, matzo meal or flour, kosher salt, and black pepper. Mix thoroughly until ingredients are evenly incorporated.
03 -
Heat vegetable oil in a large skillet over medium-high heat to a depth of about 1/4 inch. Once the oil is shimmering, scoop about 1/4 cup portions of the potato mixture and flatten gently. Fry latkes in batches, cooking 3 to 4 minutes per side until deeply golden and crisp. Drain on paper towels.
04 -
Combine egg yolks, lemon juice, and kosher salt in a heatproof bowl. Set over a pan of gently simmering water and whisk continuously until mixture is slightly thickened. Gradually pour in melted butter, whisking until the sauce is glossy and has thickened. Remove from heat and keep warm.
05 -
Fill a saucepan with several inches of water and bring to a gentle simmer. Add a splash of white vinegar. Crack the eggs one at a time into a small bowl, then gently slide each egg into the water. Poach eggs for about 3 minutes, until whites are set and yolks are just runny. Lift out with a slotted spoon and drain briefly on paper towels.
06 -
Arrange two latkes per serving plate. Top each latke with a slice of smoked salmon, then carefully place a poached egg on top. Spoon warm hollandaise sauce over each poached egg. Garnish with finely diced red onion.