Serve this spinach salad with steak, burgers, or goat cheese and crusty bread.
In a large skillet, heat extra-virgin olive oil over medium-high. Add minced shallots, and cook, stirring often, until softened, about 3 minutes. Season with coarse salt and pepper. Reduce heat to medium-low and cook, stirring, until shallots are sticky and browned, about 8 minutes. Add water and cook, stirring and scraping up browned bits from skillet, until shallots are dark brown, 3 to 5 minutes. Remove skillet from heat; add whole-grain mustard and red wine vinegar and stir to combine. In a large bowl, place 2 bags (10 ounces each) baby spinach and pour warm dressing over top. Add 1 teaspoon vinegar, toss, and season with salt and pepper.