Rough chop your Prosciutto and put it with the onion, galic and the butter or oil in a frying pan or saute pan over medium heat.
Add the Brussel Sprouts and lightly saute till a little bit browned on the edges.
Add mushrooms and lightly saute them, sprinkle the salt and pepper over lightly. (I generally add a pinch of sea salt and a generous pinch of fresh cracked pepper)
Add the chicken stock and put a lid on, lower the heat and simmer for a few more minutes till the Brussel Sprouts are cooked thru but still firm. Drain and remove to serving dish. This can be served with a sprinkling of fresh grated parmesan cheese or it stands alone just fine.