Begin by grating the russet potatoes and yellow onion into a large bowl. Submerge them in lightly salted water for 20–30 minutes to draw out excess starch. Once the time is up, drain the mixture thoroughly and squeeze out any remaining moisture.

In the same bowl, combine the drained potato-onion mixture with the lightly beaten egg, matzo meal, kosher salt, and freshly ground black pepper. Stir until the mixture is cohesive and well-blended.

Heat a generous amount of vegetable oil in a large skillet over medium heat until it shimmers. Form the latke mixture into 3-inch rounds and carefully place them in the hot oil. Fry each side for about 6–10 minutes or until golden brown and crispy.

In a medium saucepan, bring water to a gentle simmer and add a splash of white vinegar. Create a whirlpool and gently slide in the eggs. Poach for 4½ to 5 minutes for runny yolks.

In a blender, combine egg yolks, fresh lemon juice, and a pinch of salt. While blending, slowly drizzle in melted butter until it emulsifies into a thick, creamy hollandaise sauce.

To plate, start with a crispy latke, layer on smoked salmon if desired, then add a poached egg. Drizzle hollandaise sauce over the top and finish with fresh chives, flaky salt, and freshly ground black pepper.