For the sage hollandaise sauce, whisk the eggs yolks with the water and salt in a small pot for 1 minute. Place the pot over low heat and whisk constantly for 2 minutes. Add the butter, 1 tablespoon at a time, allowing each tablespoon to melt before adding the next, whisking constantly. Once you have only 4 tablespoons of butter left, add a splash of the lemon juice and alternate between adding the lemon juice and butter until all is added and smooth, whisking constantly. Once the sauce has thickened, remove it from heat and continue whisking for 2 minutes. Cover and set it aside.
For the eggs benedict, arrange the cheese, proscuitto, and tomato on each of the English muffins. Set aside. Bring a small pot of water to a boil with a splash of vinegar. Crack open an egg into a small bowl, and use the bowl to drop the egg into the boiling water. Use a spoon to help hold the yolk in the center of the egg white area. Once the egg whites have cooked but the yolk is still wobbly, remove the poached egg with two spoons (the extra support on both sides will help keep the yolk from splitting open) and transfer to one of the english muffins. Repeat with the 3 remaining eggs, then top each one with a generous scoop of the sage hollandaise and serve.