Stuffed Flank Steak with Marsala Mushroom Sauce

5 tablespoons butter divided

1 cup onion minced

2 each garlic cloves chopped

12 ounces ground pork

4 ounces pancetta chopped

1/2 cup spinach chopped

3 tablespoons currants

2 tablespoons parsley leaves chopped

1/4 teaspoon thyme

1/4 teaspoon basil

2/3 teaspoon salt and black pepper

1 each egg slightly beaten

1 large carrot julienned

1/4 pound provolone cheese julienned

2 tablespoons olive oil

2 cups beef stock prefer veal stock if possible

1 cup marsala sauce

1/2 pound mushrooms sliced

2 tablespoons lemon juice

1 ounce mushrooms, porcini soaked, sliced

1/2 cup water hot

1 tablespoon cornstarch

2 tablespoons marsala wine