Peel or scrub the Russet potatoes and peel the onion. Grate both on the large holes of a box grater or in a food processor. You want long, visible shreds, not a paste.

Pile the grated potatoes and onion into a clean kitchen towel. Gather the towel into a bundle and squeeze firmly over the sink or a bowl until very little liquid drips out. The shreds should feel damp but not wet; this is what helps the mini latkes turn crisp instead of soft.

Transfer the squeezed shreds to a large bowl. Add the eggs, kosher salt, black pepper, and potato starch or flour. Mix until everything is evenly coated and the mixture holds together in loose clumps. There should be no puddle of liquid at the bottom of the bowl.

Pour about ¼ inch of neutral oil into a large skillet and set it over medium heat. When a small pinch of the mixture sizzles on contact and tiny bubbles form around it, the oil is ready.

Drop small spoonfuls of the potato mixture into the hot oil, about 1½–2 inches wide. Flatten gently with the back of the spoon into small rounds. Fry 2–3 minutes per side, until deeply golden and crisp, then transfer to a rack or paper towel–lined tray. Sprinkle lightly with salt while hot. Repeat with the remaining batter, skimming out any dark bits from the oil as needed.

Keep finished mini latkes on a rack in a 250°F oven while you fry the rest. To build the board, place small bowls of sour cream, applesauce, and any dips on first. Arrange the mini latkes around them in clusters, then add smoked salmon, cucumbers, radishes, pickled onions, herbs, roe, capers, honey, and lemon wedges in the gaps. Serve warm or at room temperature.