Mince and cheese pie recipe

Name: Mince and cheese pie recipe
Prep time: 1 h
Cook time: 25 min
Total time: 1 h 25 min
Cuisine: European, British
Ingredients: 2 tbsp cooking oil; 1 Onion (Finely diced); 1 Stick celery (Finely diced); 2 Garlic (Finely diced); 500 g Ground beef mince; 1 Carrot (Finely diced); ½ tsp Thyme dried; ½ tsp Rosemary dried or 1 fresh rosemary spring; 1 Bay leaf; 2 tbsp Tomato paste; 1 tbsp Mustard; 2 Tbsp Worcestershire sauce; 2 tbsp Plain flour; 1 ½ cups beef stock; Salt and pepper; 4 slices cheddar cheese; 4/6 Sheets pre-rolled puff pastry (Frozen or fresh (See note 1)); 1 egg (beaten)