Begin by grating the russet potatoes and yellow onion using a box grater or food processor. Transfer the grated mixture into a bowl filled with salted water and allow it to soak for up to an hour.

Once soaked, drain the potatoes and onion thoroughly in a colander. Wrap the mixture in a clean kitchen towel and squeeze firmly to remove excess moisture.

In a large mixing bowl, combine the drained potato-onion mixture with eggs, matzo meal (or all-purpose flour), kosher salt, and black pepper. Use a fork to mix until well combined.

In a large skillet, pour in enough vegetable oil to create a shallow layer about 1/4 inch deep. Heat the oil over medium-high heat until it shimmers.

Spoon generous amounts of the latke mixture into the hot oil, forming 3-inch rounds. Fry for 6-10 minutes on each side until golden brown and crispy.

In a pot, bring water to a gentle simmer and add a splash of vinegar. Crack each egg into a small bowl, then gently slide it into simmering water. Poach for 4-5 minutes until the whites are set.

In a heat-proof bowl, whisk together egg yolks, fresh lemon juice, and a pinch of salt. Place over a pot of simmering water and slowly whisk in melted unsalted butter until thickened.

To assemble, place one crispy latke on a plate, layer with smoked salmon, top with a poached egg, drizzle with hollandaise, and garnish with chives and red onion.