Directions

1. In a small bowl, whisk together the balsamic vinegar, olive oil, mustard, salt and pepper to make the dressing. Set aside.
2. Place the pine nuts in a dry skillet over medium heat. Cook and stir for a few minutes, just until they are fragrant and lightly toasted. Set aside to cool.
3. Cook bacon in a large skillet over medium-high heat until evenly browned and crisp. Remove bacon to paper towels to drain. Reserve a thin layer of bacon grease in the pan. Stir in about 1/4 cup of the dressing, and turn the heat to medium. Add the onions; cook, stirring occasionally, until caramelized, about 20 minutes.
4. Reduce the heat to low, and crumble the bacon into the pan. Stir in the remaining dressing, and heat through.
5. Place the spinach in a large bowl. Pour the warmed dressing with bacon and onion over the spinach, then sprinkle with pine nuts and gorgonzola cheese.