Bring a wide saucepan of water to a gentle simmer. Stir in the vinegar. Crack each egg into a small cup, then slide it into the water. Poach in batches for 3 to 4 minutes for set whites and soft yolks. Lift out with a slotted spoon and drain on a clean towel.
Toast the English muffin halves. Warm the Canadian bacon in a skillet over medium heat for about 1 minute per side, until hot.
For the hollandaise, blend the egg yolks and lemon juice until slightly thickened. With the blender running, slowly drizzle in the hot melted butter until the sauce is smooth and creamy. Blend in cayenne and salt. If too thick, blend in warm water 1 teaspoon at a time.
Set one slice of Canadian bacon on each muffin half, top with a poached egg, and spoon hollandaise over it. Finish with chives and serve immediately. Keep the sauce warm, not boiling.