Cottage pie, like its opposite lamb number, Shepherd's pie, was the ingenious idea of housewives many years ago, in order to create another warm and comforting meal usually from the Sunday Lunch left-overs! Cooked beef or lamb were diced or shredded and sometimes the vegetables were added to the meat mixture - such as peas or carrots. This recipe uses raw minced beef, but you could use minced cooked beef if you wish, I have added it as an alternative. The leeks were always added to the mashed potato topping when I was growing up - it was another way of utilising the leftovers! A bit like a Bubble and Squeak topping. I am not a lover of peas being added in my Cottage Pie, so I have suggested them as an option - I always prefer carrots as the vegetable to be added. Try to use mature Farmhouse Cheddar cheese for the topping - a little goes a long way, as it is so strong in flavour. The cheese is very luxurious, but takes this simple and comforting pie to a higher taste level, in my humble opinion! Serve bubbling hot straight from the oven with steamed cabbage, carrots or any seasonal vegetables and a jug of gravy.