In a large mixing bowl, combine the spinach, chopped pecans, and Swiss cheese.
In a large skillet, sauté the onions and garlic in olive oil until soft. Add the chopped bacon, vinegar, mustard, and honey. Stir until thoroughly mixed and the dressing is starting to boil.
Pour the hot dressing over the spinach leaves and toss everything together until the ingredients are distributed evenly and the spinach leaves are thoroughly coated.
Serve and enjoy!