melt butter in olive oil in a medium size pan. finely chop onion, garlic and prosciutto and saute in olive oil and butter over medium heat until onion is translucent, about five minutes.
add arborio rice and stir over medium heat for a few minutes so that each grain gets coated with the oil and butter mixture. add salt and pepper.
add one cup of the chicken broth and stir often until it is absorbed. as broth is absorbed, add another cup. after about 20 minutes, add the white wine and another cup of broth. add the grated cheese and a 1/2 cup of broth. stir until cheese is melted and correct seasoning. serve immediately.