Bring a small saucepan with enough water to cover the egg to a rolling boil. Place cold egg into water and bring back to a rapid boil and cook like so for 30 seconds. Lower heat to simmer for 5½ minutes, then transfer egg to an ice bath to halt cooking. Once cool enough to handle, peel and set aside.

Slice bagel in half and toast until slightly golden on cut sides. Slather halves with yogurt or creme fraiche. Arrange salmon slices on top, followed by the sliced beet and chervil. Slice the egg in half and divide onto plates. Spoon pickle brine with mustard seeds onto beet slices and crack pepper over all. Keep in mind both the salmon and caper-berries impart saltiness, so taste without adding salt at first to see, adding salt to taste as needed.