Heat a grill or grill pan to medium-high heat. Place the bread on a baking sheet and brush both sides with olive oil. Grill the bread until golden all over, 2 to 3 minutes per side. Rub one side of each with the garlic clove.
Spread a tablespoon or two of the ricotta on each bread slice, then press an arugula leaf into the cheese. Place a slice of the prosciutto on top, drizzle with the best quality olive oil, and serve.
Recipe courtesy Ted Allen, "In My Kitchen: 100 Recipes and Discoveries for Passionate Cooks," (Clarkson-Potter)