Place rinsed spinach and mushrooms into a large salad bowl and put in refrigerator. Place a large skillet over medium-low heat and fry bacon until it is crispy but still slightly tender. Transfer bacon to a paper towel-lined plate and set aside.

Remove all but 3 Tbsp of bacon grease from the skillet and return to heat.

Add red wine vinegar, Dijon mustard and honey, and stir to combine. Season to taste with salt and pepper. Remove dressing from heat and set aside to cool slightly while you chop or crumble bacon into small pieces.

Remove spinach and mushrooms from refrigerator and add crumbled bacon and pickled onions. Drizzle desired amount of dressing over salad and toss to coat. Transfer salad to a serving dish and season with salt and pepper. For an unexpected bit of sweetness and additional crunch, sprinkle dried cranberries and sunflower seeds over the top. Be sure to add a few slices of hard-boiled eggs to each serving and enjoy!