Cheese and leek toastie

Name: Cheese and leek toastie
Prep time: 10 min
Cook time: 15 min
Total time: 25 min
Yield: 2 servings
Cuisine: British
Ingredients: 100 gr of Grated mild cheddar cheese; 1 Leek; 4 slices of Sourdough bread; 1 slice of Unsalted butter; ½ tsp of Wholegrain mustard