Blue Cheese

5 ounces of thick cut pancetta, cut into ½, 1 large onion, peeled and chopped, 1 clove garlic,

3 tablespoons unsalted butter, 3 leeks, washed and sliced using all of the white part and a

1.5 pounds flank steak, ⅓ cup red wine vinegar, ⅓ cup olive oil, 1 T fresh rosemary, finely cho