Slow Cooker Flank Steak

1.5 pounds flank steak, a.k.a. London Broil
2Tbsp cooking oil of choice, I used olive oil but you can use coconut oil too
1 large onion, I used yellow
1.25tsp chili powder
1tsp garlic powder
1/2tsp salt
1/4tsp pepper
1/3cup water
2Tbsp white vinegar
Handful mushrooms of choice, I had buttons on hand
Remove silver skin and excess fat from the meat. In a skillet set to medium-high heat, heat oil to almost smoking. Make sure the pan and oil are nice and hot and brown both sides of the meat. I cut mine in half and browned separately since my pan was too small. I placed it into my slow cooker so that it would have all the juices instead of adding to another pan or plate. Think ahead, think smart! Once it's browned one both sides, move it to the slow cookers and add the sliced onion to the pan. Add more oil if needed. Directions said to cook about 1 minute but I cooked it 3-4 minutes while I was gathering my spices. Add the water, vinegar and spices and bring to boil then cover the flank steak with this mixture. At this point, I added the mushrooms. You'll cover without removing the lid on your slow cooker. Trust me, don't peek inside! It needs the moisture especially with a tough cut of protein like flank steak. Cook for 4 hours, which is a high setting on my cooker and it will come out perfect!