Toast your English muffin in the toaster. Add the slices of mozzarella cheese on top of each half and then top with the fresh basil leaves.
To make the poached eggs, bring 2 small pots of water to a simmer. Meanwhile, crack your eggs into 2 separate bowls. Add 1 tablespoon of vinegar into each pot and stir to create a "whirlpool" in each pot of water. Drop an egg into the center of the whirl pool and let simmer for 4 minutes. You can cook each egg 1 at a time i the same pot of water if you wish but I do it in the 2 to save time. Remove poached eggs with a slotted spoon and set down on a dish to rest for a couple minutes then place on top of the prepared English muffins. Salt and pepper to taste. Leave 1 pot of simmering with water for the next step.
To make the hollandaise sauce, place the egg yolk in a metal bowl and whisk. Add the hot water and continue whisking. Add the lemon juice, salt and butter and place over the simmering pot, creating a double boiler (bain marie). Whisk until the butter has melted and then continue whisking until the sauce begins to thicken. Once you achieve the desired thickness, spoon hollandaise sauce on top of the eggs.