In a glass measuring cup, combine egg yolks, lemon juice, salt and pepper. Blend with an immersion blender until pale yellow, about 30 seconds. Alternatively, use a blender.
With the blender running, slowly pour the hot butter into the yolks and blend until thick.
Preheat oven to 375°F.
Line two baking sheets with foil. On one sheet, shape each prosciutto slice into a circle and bake until crispy, about 15 minutes.
On the other sheet, arrange ciabatta slices in an even layer. Drizzle with 2 tablespoons olive oil, season with salt and pepper, and toss to coat. Bake for 8- 10 minutes, or until bread is golden brown on the edges but still springy in the center.
Meanwhile, poach eggs and make hollandaise sauce.
To assemble benedict, place two slices of toasted ciabatta on a plate. Top each piece of bread with a slice of crispy prosciutto, a slice of tomato, a few basil leaves and a poached egg. Drizzle with hollandaise sauce and serve.