1. Preheat skillet on medium heat. Add mushrooms and onions. Stir infrequently to allow mushrooms to brown on pan. Add garlic and sauté for a few more minutes. Add a splash of water or vegetable stock as necessary if too much sticking occurs. Deglaze pan with white wine. Cook off wine.
2. While mushrooms and onions are sautéing, add all remaining ingredients to blender. Blend until smooth.
3. Add cashew sauce mixture to pan with mushrooms. Cook until sauce is warm and thickened to desired consistency.
4. While sauce is warming, toast bread. Serve on toast.