Cook the bacon or ham in a large skillet as you normally would. set aside.
While the bacon is cooking, fill a large saucepan 2/3 of the way up with water and bring to a boil. Add the vinegar, then lower the temperature so it's at a light simmer.
For the Hollondaise sauce, fill the bottom of a double boiler part-way with water, and bring to a simmer. On the top half of the double boiler, whisk together egg yolks, lemon juice, white pepper, Worcestershire sauce, and waer.
Add the melted butter to the hollondaise mixtures 1 or 2 tablespoons at a time while constantly whisking the yolks (this part is very important for a proper Hollondaise). Add small amounts of water to the Hollondaise if it starts to get too thick.
After slowly adding in all the butter, whisk in the salt then remove from heat. Cover with a lid to keep warm.
Toast your English muffins.
Poach the eggs by carefully cracking the egg into the water. Allow the egg to begin to solidify before adding another. Keep track of what order you put the eggs in, as you will want to pull them out in that order.
Let the eggs sit for 3 1/2 to 4 minutes before removing from the water with a slotted spoon.
See if you can get everything ready at the same time (having a second person in the kitchen helps) and assemble.
Butter an English muffing half, top with bacon or ham, add a poached egg on top of the bacon, pour Hollondaise sauce over, sprinkle with parsley or scallions.