Combine the mushrooms, onion, cauliflower, thyme, red pepper flakes, vinegar and salt to taste in a bowl. Toss well to combine, cover and let sit outside of the fridge for at least an hour, stirring once or twice. This will sort of cook the veggies and lightly pickle them.
Preheat the oven to 375 degrees F. On a large baking sheet lined with a silicone mat or parchment paper, make 4 flat circles of parmigiano-reggiano. Bake 8 to 9 minutes, or until the cheese looks golden and lacy. Remove the cheese rounds from the oven and let cool on the baking sheet for 1 to 2 minutes, then loosen them with a spatula. Let cool completely.
Divide the prosciutto among 4 plates. Toss the mushroom mixture with the arugula and a drizzle of big fat finishing oil. Taste to make sure the mix is delicious. Arrange a pile of the veggie mix on top of the prosciutto on each plate. Crumble the parmigiano disks on top.
Photograph by Lisa Shin
Recipe courtesy Anne Burrell for Food Network Magazine