Preheat the oven to 400 F.
Place mushrooms in the remaining marinade, top side down and bake, uncovered, for 20 minutes. Remove from oven, flip, and bake another 5-10 minutes until mushrooms are cooked all the way through.
Optional - Once mushrooms are finished baking, heat a cast iron griddle over medium-high heat. Place mushrooms, top side down on hot skillet and brown for 2-3 minutes until steaks are slightly charred.
Serve with roasted potatoes and grilled vegetables.
If you'd rather grill these steaks, follow these instructions.