Potato Shepherd'S Pie

Ingredients

• 6 None large uniformly-sized potatoes
• 2 tbsp butter, at room temperature
• 2 tbsp vegetable or olive oil
• 1 None large yellow onion, finely chopped
• 2 None cloves garlic, finely chopped
• 14 oz ground lamb
• 2 None small carrots, finely chopped
• 2 None celery sticks, finely chopped
• 2 tbsp tomato paste
• 2 tbsp Worcestershire sauce
• 2 oz Cheddar cheese, grated