Wrap each skirt steak with 4 slices of bacon, then place in a square glass dish. Refrigerate up to 24 hours.
Melt 2 tablespoons of the butter in a large skillet. Add the shallots and cook over low heat, stirring, until softened, about 5 minutes. Add the mushrooms, season with salt & pepper, cover and cook until they have released their liquid, about 4 minutes. Uncover and cook over medium heat until the mushrooms are browned, about 7 minutes longer. Add the remaining 1 tablespoon butter and cook, stirring, for 1 minute. Season with salt & pepper and transfer to a bowl.
Remove the bacon slices from the steak and discard. (If the steaks are coiled, remove the wooden skewers and uncoil, so they will cook evenly). Heat 1 tablespoon of the garlic olive oil over medium-high heat in a large skillet. Add the steaks and cook until browned on the bottom, about 6 minutes. Turn the steaks and cook until medium-rare, about 6 minutes longer. Transfer the steaks to a carving board and let rest 5 minutes.
Return the mushrooms to the skillet and gently reheat, scraping up the browned bits and stir in the parsley. Thinly slice the steaks and arrange on plates. Top with the mushrooms and serve.