Step 1

To prepare the dressing, combine all the ingredients except for the oil and oregano in the jar of a blender. Blend until smooth, then, with the blender running, add the oil in a steady stream. Turn off the blender, add the oregano, and pulse 2-3 times or until combined. Set aside.

Step 2

Heat the vegetable oil in a large skillet over medium-high heat. When hot, add the prosciutto and cook until brown and crispy. Remove with a slotted spoon and drain on a paper towel. Set aside.

Step 3

In a large bowl, toss the lettuce, cheese, onions, and crispy prosciutto. Lightly drizzle some of the dressing on the salad and toss until combined. Serve immediately with additional dressing on the side, refrigerating any dressing leftovers.