Astounding Eggs Benedict

FILL a wide pot 2 in. deep with water and bring to a simmer. Whisk yolks with yogurt, butter, Dijon, zest and salt in a medium heatproof bowl and place over water. Cook, whisking constantly, until mixture thickens and yolks are cooked, 7 min. Remove bowl from heat. Toast muffins. ADD vinegar to simmering water. Crack an egg into a small dish, then slip into water. Repeat with remaining eggs. Adjust heat so water gently simmers. Cook, uncovered, until whites are set and yolks are done as you like, 3 to 6 min. It’s best if yolks are runny. PLACE a muffin half on each plate. Top with spinach, then smoked salmon. Using a slotted spoon, remove poached eggs. Dab whites with paper towel to absorb water, then place an egg on each muffin. Whisk yogurt sauce and spoon overtop. Season with fresh pepper and sprinkle with chives.