Wilted Spinach Salad with Pickled Shallots and Sherry Vinaigrette

Name: Wilted Spinach Salad with Pickled Shallots and Sherry Vinaigrette
Ingredients: 3 tablespoons sherry vinegar; 1 teaspoon salt; 1/2 teaspoon freshly ground black pepper; 1 tablespoon Dijon-style mustard; 1/2 cup extra virgin olive oil; 2 bunches spinach, leaves only, well washed and dried; 10 pickled shallots (recipe below), slivered; 1/2 cup pepitas (see note); 1/2 cup crumbled feta or anejo cheese (optional); 20 medium shallots, unpeeled; 1 cup red wine vinegar; 1 cup dry red wine; 1/2 cup sugar; 1 tablespoon mustard seeds; 2 tablespoons black peppercorns; 2 teaspoons red chile flakes; 2 tablespoons Kosher salt