Poach the eggs. Follow these sure-fire instructions to get the perfect poach.

While the eggs are poaching, toast each half of the English muffin and make the vinaigrette.

To make the vinaigrette, combine the lemon juice, Dijon, olive oil, salt, and pepper in a food processor and puree for a few seconds until creamy and combined.

Assemble the sandwiches. Top each half of the English muffin with a bit of arugula, one slice of prosciutto, and a poached egg. Right before serving, top each egg with a teaspoon or two of the vinaigrette.