In a large skillet over medium low heat. Add the sliced Canadian bacon. Cook slowly turning occasionally, until browned on both sides. Remove from the pan and keep warm on a covered plate.
Meanwhile, bring a large saucepan of water to a boil, then add the vinegar. Bring back to a boil, then lower the heat to a low simmer.
As the water comes to a boil, make the Hollandaise sauce. Add 3 egg yolks, a tablespoon of lemon juice, and 1/2 teaspoon salt in a blender. Process medium high speed for 20-30 seconds, until the egg mixture is light in color.
Melt 10 tablespoons unsalted butter. Turn blender down to lowest setting and slowly drizzle in the hot melted butter, while continuing to blend. Transfer sauce to a container you can use for pouring and set it on a warm—but not hot—place on or near the stovetop.
To poach the eggs, first crack each egg into four separate bowls. Working with one egg at a time carefully slide it into the barely simmering water. Once it begins to solidify, you can add another egg, until you have all four cooking.
Turn off the heat (remove from heat if using an electric stovetop), cover the pan, and let sit for 4 minutes.
Remove the eggs by gently lifting out with a slotted spoon.
Note that the timing is a little variable on the eggs, depending on the size of your pan, how much water, how many eggs, and how runny you like them. You might have to experiment a little with your set-up to figure out what you need to do to get the eggs exactly the way you like them.
Once you've added the last egg to the poaching water, begin toasting your English muffins.
Assemble your Eggs Benedict
Butter one side of an English muffin.
Top with 1 slice of Canadian bacon.
Place a poached egg on top of the Canadian bacon.
Pour Hollandaise over the egg.
Sprinkle with fresh chopped parsley and serve immediately.