I like to wash and spin all the greens in very cold water. After draining, I put the bowl in the refrigerator to chill while the rest of the ingredients are prepared.
Start a pot of water over medium-high heat. Once the water is boiling, gently add 6 eggs and set a timer for 7 minutes.
After 7 minutes, remove the eggs and add to a bowl of ice water. Once the eggs have lost some heat, about 5 minutes, remove from ice water.
Tear the prosciutto slices into bite-sized pieces, keeping in mind that the pieces will shrink when cooked.
Add 1 tablespoon of olive oil to a non-stick skillet, medium heat. Add the pieces of prosciutto to the hot oil. It only takes about 1 minute a side to crisp the prosciutto pieces. After the pieces have fried in the oil for a total of 2 minutes, remove to a paper towel to drain.
Peel and cut red-skinned potatoes into ⅜-inch dice. Add a tablespoon of olive oil to the pan you used for the prosciutto. Make sure to salt and pepper the potatoes after adding them to the oil. Have the heat at medium and cover the pan with a lid to soften the potatoes. Occasionally shake the pan to redistribute the potatoes. After 5 minutes, add the shallot slices and 1 tablespoon of olive oil.
After 5 minutes, the potatoes should be browned and the shallots should be soft. Turn off the heat. Add 2 tablespoons of whole grain mustard and 2-3 tablespoons of sherry vinegar to the pan. The amount of vinegar is up to you - 3 tablespoons may be too much for some people. The addition of mustard and vinegar to the vegetables will somewhat deglaze the bottom of the pan, which is good. You want all that flavor!
Add 2-3 tablespoons of olive oil to the pan. Combine with the potatoes, shallots, and vinaigrette ingredients.
Let the potatoes cool while you peel the soft-boiled eggs.
Remove the greens from the refrigerator and season with salt and pepper. Toss with the fennel and the crispy prosciutto.
Add the potatoes and shallots to the greens, tossing to combine. Lastly cut the soft-boiled into halves or quarters and add to the salad. You may want to cut the eggs open over the salad because the yolk will be runny. The yolk will coat the salad greens, becoming part of the vinaigrette.