Skirt steak is known for its strong beefy flavor and is typically found in Mexican fajitas and Philadelphia, or Philly, cheesesteak sandwiches. Compared to strip or rib eye steaks, skirt steak generally costs about 50 percent less. Keep in mind it tends to toughen up if it's cooked to more than medium doneness.
Purchase two 4-oz. pieces of skirt steak, or cut your own 4-oz. pieces from a larger piece.
Season the steak with salt and pepper to taste. For more flavor, place the steak in a bowl and pour a marinade of soy sauce, ginger and garlic over it. Cover the bowl with plastic wrap and allow it to sit for 10 to 15 minutes.
Preheat oven to 450 degrees Fahrenheit and place a large, empty pan or stir-fry skillet in the oven.
Spray a second pan with olive oil cooking spray and set it on the stovetop over medium-high heat. Add the mushrooms, and occasionally toss them around in the pan while they brown. They will start to caramelize in about 15 minutes. Then add the olive oil and onion. Toss once or twice, then add butter, salt and pepper. After three or four more minutes, add thyme, stir well, remove from heat and set aside.
Remove the pan from the oven and spray lightly with olive oil. Place the skirt steak in the pan and return to the oven for 6 to 9 minutes, depending on how well done you like your steak. Then, flip the steak over and bake for half the time it cooked on the first side.
Place the steak on a serving platter and spoon the sauteed mushrooms on top.