1) Chop rough stems off spinach and roughly chop. Also, thinly chop radicchio. Add both to a salad spinner and rinse well. Then spin to dry. Set aside for later.
2) In a large skillet, add a small drizzle of oil and chopped bacon over medium heat. After the fat starts to render out of the bacon, add chopped shallot and cook for 3-4 minutes until bacon starts to crisp up.
3) Add mushrooms to the skillet along with 1/4 cup water to help the mushrooms break down. Cook until mushrooms lose their liquid, 4-5 minutes. Season with salt, pepper, and a pinch of dried rosemary.
4) Take the mushrooms off the heat and stir in white wine vinegar, olive oil, and sugar.
5) Divide spinach and radicchio between plates and drizzle with warm mushroom mixture. Serve immediately!