- Combine yolks and juice in a heatproof bowl; set over a pot of simmering water. Rapidly whisk until the yolks are light, thickened with ribbons running through them, and feel quite warm (this will take a few minutes; do not overcook or yolks will scramble).
- Remove bowl from the heat and set on dampened tea towel so it does not move around. Now very, very slowly dribble and whisk in the butter. Now mix in the pesto. Cover this hollandaise sauce and set aside until needed. You should have about 1 cup of sauce.
- Fill a very large and wide pot 2/3 full with water. Add the vinegar and bring to a simmer.
- As the water comes to temperature, set an oven rack 6” underneath your broiler. Preheat broiler to high. Set bread on a baking sheet and brush the top of each slice with olive oil. Now sprinkle each slice with Parmesan cheese. Broil bread until lightly toasted, 1 to 2 minutes, and then remove from the oven.
- Turn oven temperature to 200˚F. Now top each bread slice with 2 slices tomato and 1 slice of prosciutto. Set the top bread in the oven to warm.
- When simmering, swirl the water and then crack eggs into it. Poach eggs to the desired doneness (about 3 minutes for soft poached).
- Set 2 slices of bread on each of 4 plates. Now top each piece of bread with some of the arugula. Lift eggs out of the water, drain well, and set one on each piece of bread. Top with hollandaise sauce and serve, garnishing each plate with a few basil leaves, if desired.
Recipe Options: If time is short cheat and use packaged hollandaise sauce mix in this recipe. Instead of proscuitto, top each bread slices with 2 thin slices of pancetta, that you’ve fried until crispy. You can buy pancetta, a cured Italian-style of bacon that’s not smoked, in our Deli Department showcase.