Skirt Steak rolled w Mushrooms and Ginger

No picture tonight, but then this is more of a note-to-self since I was surprised by how much I liked this spontaneous concoction tonight.

Skirt steak (just under 1 lb)
1 tbsp butter
1 yellow onion
Large handful mixed mushrooms
1 tbsp fresh, finely minced ginger
fresh flat-leaf parsley, finely chopped
apple cider vinegar
olive oil
salt and pepper

Peel your onion, cut in half, and slice into very thin half-rings. Clean the mushrooms (I used white button and "baby bella" mushrooms) and slice very thinly. Note: our skirt steak was quite small - fine for two people, but if you are making a larger amount, increase the amount of onion, mushrooms and ginger.

Melt a tbsp of butter and a splash of olive oil in a saute pan on low heat, and then cook the onions until they turn translucent. Add the mushrooms and continue cooking on low heat until everything is well cooked. Add a small pinch of salt and stir in the ginger. Cook for a minute or two then remove from heat.

Cut the skirt steak into two 8-to-10-inch long strips (our skirt steak was about 4 inches wide). Tenderize with a mallet to thin and widen the meat. Sprinkle salt, pepper and parsley on each strip, then add a layer of the mushroom mixture to the top.

Roll each steak strip up tightly and tie each roll at both ends with two lengths of wet kitchen string.

Sear the rolls on two sides quickly on a grill or under a broiler (hence wetting the kitchen string), then transfer to a small baking dish. Drizzle a little olive oil and a tsp of apple cider vinegar on each roll, then place in an oven set to 350F for 10 to 15 minutes. Remove string and serve.