In a large skillet over medium heat, melt one tablespoon of butter. Add the onions and peppers; saute for several minutes until softened. Add the mushrooms and one tablespoon butter; saute for several minutes until browned.
Add the kale, garlic, and balsamic vinegar. Saute until the kale is deep green but not yet wilted. Remove from heat and serve topped with Asiago or Parmesan cheese. Season with salt and pepper to taste.
You can also add a protein for a more filling "meal" salad, like grilled salmon, chicken, white beans, etc. I also liked having this over a brown rice/ancient grain blend.
Recipe by Pinch of Yum at http://pinchofyum.com/warm-balsamic-kale-salad