For the hollandaise sauce: Melt the butter over low heat in a small pot - do not let it boil. In a bowl, whisk the egg yolks and lemon juice; season with salt and pepper. Slowly drizzle in the melted butter while whisking. (The sauce should be thick, buttery, lemony and just lightly salty. If it is not salty or lemony enough, you can add a little lemon juice or salt to taste.) Mix in chopped parsley. Set aside.
Fill a saucepan with water. Bring the water to a low simmer. Stir the vinegar into the water.
Crack the eggs into a bowl. Gently place the eggs into the water. (You can poach multiple eggs at once, being careful not to overcrowd the pan.)
Cook the eggs in the water for 3-4 minutes. Remove the eggs with a slotted spoon. Season with salt.
Toast the English muffins, top with poached eggs, hollandaise sauce, and salmon. Garnish with capers and parsley. Serve with raspberries.