Leftover Turkey Sandwich Recipe

Ingredients

• ½ large white onion, finely chopped
• 2 tablespoons white wine vinegar
• 2 tablespoons lemon juice
• 4 teaspoons dijon mustard, divided
• fine sea salt, to taste
• black pepper, to taste
• ⅓ cup olive oil
• 1 tablespoon fresh dill, finely chopped
• ¼ cup sour cream
• 1 lb leftover turkey, chopped into 1/2-inch (1 cm) pieces
• 8 slices swiss cheese
• 1 small head little gem lettuce, leaves separated, cleaned, and dried
• 8 slices pullman loaf, or white bread