Heat 1 tablespoon oil in a large skillet over medium heat. Add bacon and shallot and cook, stirring, until the bacon is crisp, 4 to 5 minutes. Add mushrooms, salt and pepper and cook, stirring, until the mushrooms are tender, 5 to 7 minutes. Remove from heat and stir in the remaining 1 tablespoon oil, vinegar and honey, scraping up any browned bits. Immediately pour the warm vinaigrette over the spinach mixture and toss to coat.