Marinated Flank Steak with Mushrooms

2 pounds grass-fed flank steak
1/2 cup red wine (sometimes you just need wine)
1/2 cup coconut aminos
6 cloves garlic, minced
1 tsp black pepper
1 pound crimini mushrooms, sliced
1 tbsp butter or ghee
chopped green onion

Combine the wine, coconut aminos, garlic and pepper in a dish large enough to fit the steak. Add the steak and turn to coat. Refrigerate for at least 1 and up to 4 hours. Remove the steak from the marinade, reserving the marinade, and grill or broil the steak on high heat about 4 minutes per side for medium rare.

Allow to rest for 10 minutes, then slice thinly against the grain. Transfer to a serving platter and keep warm.
While the steak is resting, prepare the mushrooms: Heat a large skillet over medium heat and melt the butter. Add the mushrooms and brown on both sides. (you may have to do this in 2 batches so they can brown)
Add the reserved marinade and reduce until it is reduced to roughly 1/2 cup. Pour the mushrooms and sauce over the steak, top with green onion and serve.