In a saucepan or skillet, fry the bacon until crisp. Remove and place on a paper towel. Chop the bacon into small pieces. Remove 3 of the tablespoons of bacon grease and set aside.
Use a small amount of the bacon grease to sauté the onions until caramelized. Remove from pan and add the sliced mushrooms until cooked.
Mix the bacon grease, red wine vinegar, sugar, mustard & salt (to taste) in a small saucepan. Whisk together and heat thoroughly.
In a large bowl, add the mixed greens & arrange the onions, mushroom & bacon. Pour the dressing over the top and toss to combine. Arrange the eggs over the top and serve.
Source: adapted from The Pioneer Woman