Split the English muffins and toast to your liking. (Lightly toasted, gently crisp on the outside and tender inside if you're looking for a recommendation.) Divide among 4 plates.

Butter each muffin half and drape a slice of prosciutto overtop while still hot. 

To poach the eggs, fill a wide sauté pan halfway with water. (A pan like this is ideal.) Add vinegar and bring water to a brisk simmer, then reduce heat so the water is virtually still.

Crack each egg into a small bowl and tip carefully into the water, submerging the bowl a bit as you pour. I like to add the eggs in a clockwise circle starting near the handle so I remember in which order to remove them for even cooking.

Cook undisturbed for four minutes, until whites are set and yolks are runny.

Remove eggs from pan with a strainer spoon (something like this). Gently place eggs on a paper towel-lined plate and dab the tops to remove excess water. Cut away any scraggly whites if you like.

While the eggs poach, make the Hollandaise.

To serve, place a poached egg over each prosciutto-draped English muffin half and spoon some Hollandaise sauce overtop.

Finish with freshly ground black pepper and some parsley if you like. Serve right away