Bring an inch and a half of water to just below a simmer, around 200°F. Stir in the vinegar and salt.
While the water is heating, warm a small saucepan over medium-low heat. In a separate bowl, whisk together the egg yolks with a tablespoon of water. Remove the saucepan from the heat and whisk in the egg yolk mixture. Quickly mix in the lemon juice, cayenne pepper, and sugar. Make sure it's well combined. Return to the heat, but be careful. Only warm it up for 10-15 second intervals to prevent the yolks from scrambling.
Gradually add the butter, one tablespoon at a time, ensuring it melts and incorporates into the sauce between each addition. Aim for a smooth, thick consistency.
In a different skillet, sear the salmon fillets on both sides for about 1-2 minutes or until you get your preferred sear.
Create a whirlpool in the warm water. Crack an egg into a small bowl, then gently slide it into the swirling water. Let it cook to your liking: 2-3 minutes for runny yolks, 3-5 minutes for soft yolks, or 4-6 minutes for firm yolks.
Lift the eggs out of the water using a slotted spoon. Let them drain on paper towels for a moment. If needed, trim any untidy whites.
While those eggs are bubbling away, get your English muffins toasting. Once done, layer up! Start with the muffin, add your salmon (skin removed), pop on a poached egg, and generously drizzle with that amazing hollandaise you just made. Finish with some fresh parsley, an extra pinch of cayenne, and another hint of lemon juice.