Preheat oven to 450F.
Wash and trim green beans. Skip this step if using packaged French Cut Green Beans (haricots verts)
Blanch the beans- bring a large pot of water to a boil over medium-high heat. Add green beans, and cook until crisp tender, about 4-5 minutes (this may take a 1-2 min. longer if using thicker beans vs. French Cut Green Beans)
While beans are cooking fill a large bowl with ice water. Drain beans, and plunge into ice water to stop the cooking process. Drain beans, and blot dry with paper towels. Set aside.
Whisk together melted butter, garlic powder, salt, pepper, and cayenne powder in a large bowl. Add beans and toss to coat.
Gather beans into 12 bundles of approx. 12-15 beans each. Lay out 1 piece of prosciutto (which has been cut in half lengthwise) on a cutting board or other flat surface. Place one bundle of beans at end of prosciutto piece and roll up lengthwise. Place bundle, seam side down, on a baking sheet. Repeat with remaining prosciutto slices.
Bake at 450F until beans are warmed and prosciutto slices begin to brown, approx. 5-7 minutes. Serve immediately. Garnish with toasted almonds, if desired.