Step 1Combine the mustard, 2 tablespoons vinegar, shallot and the chives in small bowl and whisk to blend. Whisk in the oil. Season with salt and pepper to taste. Set aside.
Step 2Blanch the pancetta pieces in a small pan of simmering water for 10 minutes. Drain on paper towels.
Step 3Heat a small skillet over medium-high heat. Add the pancetta and cook, stirring constantly, until the fat is rendered and the meat is cooked but not crisp, 4 to 5 minutes. Remove with a slotted spoon to a plate lined with paper towels. Immediately add the bread cubes and cook, stirring constantly, until crisp, about 6 to 8 minutes. Remove and set aside.
Step 4Bring a deep skillet of water to a rolling boil. Add the remaining 1 tablespoon vinegar and one-half teaspoon salt and stir well. Reduce the heat and bring to a simmer. Break each egg into the water and poach 90 seconds. Using a slotted spoon, immediately transfer the eggs to a plate and keep warm.
Step 5Place the frisee in a large bowl and toss with the mustard dressing, pancetta and croutons. Divide among 4 serving plates. Top each salad with an egg seasoned with salt and pepper. Serve immediately.