Place onion in the bottom of your slow cooker and top with steak and garlic. I flipped my steak over half way through.
Cook for 5hrs on low
When steak is almost ready I combined the creamy garlic sauce ingredients (except the handful of grated cheese) in a measuring cup and microwaved for 3 minutes. Once combined tip over the steak and add the handful of cheese. I added this in the last 30 minutes.