Wash and pat dry mushrooms and cut them in half. Rinse and spin the greens or pat dry with a towel.
Add avocado oil to a large skillet and heat on medium-high until it begins to sizzle. Add the sausage and cook until it starts to firm up on the outside. Add the mushrooms and continue to sauté until they are browned and the sausage is fully cooked.
Add the balsamic and turn up the heat until the vinegar bubbles. Reduce to a simmer and stir. Once the vinegar thickens, remove the pan from the heat and let it cool until only slightly warm.
Mix the greens in a large salad bowl. Add 2/3 of the onion, 1/2 the tomatoes and 1/2 of the goat cheese. Pour the dressing over the salad and mix until all the ingredients are well incorporated. Be sure to get all the goodies off the bottom of the bowl.
Add the mushroom and sausage mixture right in the center as the focal point of the salad. Place the remaining onions, tomatoes, and goat cheese around the mushrooms and sausage as shown in the photo.