How to Make It
Preheat the oven to 350°. Spread the English muffins on a baking sheet and toast for about 7 minutes, until golden. Let cool.
Meanwhile, bring a large, deep skillet of water to a simmer. One at a time, crack the eggs into a small bowl, then gently slide them into the skillet. Poach over moderately low heat until the whites are set and the yolks are runny, 4 to 5 minutes. Using a slotted spoon, transfer the poached eggs to a plate.
In a large bowl, whisk the yogurt with the olive oil, mustard, lemon zest and lemon juice. Season the dressing with salt and pepper. Add the mixed greens, radicchio, ham, chives and croutons and toss to coat. Transfer to plates and top with the poached eggs. Sprinkle with pepper and serve right away.