Bring a large stockpot with about an inch of water to a simmer over medium-high heat.
Nestle a steamer basket inside the stockpot and pile in the cauliflower florets, seasoning them with a pinch of salt. Cover and steam just until the cauliflower is tender but still retains a hint of toothsome bite, about three to five minutes.
While the cauliflower steams, fill a large bowl with ice water. Once the florets are ready, use a slotted spoon to transfer them directly into the ice bath to halt the cooking. After a minute or two, move them to a towel-lined baking sheet and gently pat dry.
To make the dressing, whisk together the olive oil, red wine vinegar, oregano, basil, minced garlic and half-teaspoon of salt. Season to taste.
In a large mixing bowl, combine the cauliflower with the chopped artichokes, olives, sliced shallot and arugula, then toss with the dressing.
Chill in the refrigerator for at least 30 minutes, then mound the salad onto a serving platter. Tuck in slices of prosciutto, and serve.