Italian Style Shepherds Pie

1 large onion
25g butter
1 tablespoon sunflower oil
500g minced beef
2 large cloves garlic
250ml beef stock
2 large tablespoons tomato puree
1 tsp dried mixed herbs or oregano
salt and pepper
800g potatoes
Sauce
20g butter
2 level tablespoons flour
300 ml milk
100g grated cheddar cheese
1/2 tsp mustard
salt and pepper to taste

Melt the oil and butter together in a frying pan, add the chopped onion and cook gently until the onion is soft and starting to brown.
Increase the heat and add the mince breaking it up as you add it to the pan, fry over a medium heat stirring constantly until the meat has broken into small pieces and is a nice brown colour.
Add the crushed clove of garlic, stir.
add the tomato puree stir until well mixed
add the stock, the herbs and season.
Bring to a very gentle simmer, allow to cook until almost all the liquid has evaporated.
Meanwhile, peel the potatoes and thickly slice. Cook in boiling salted water for about 10 mins, the should be just tender when pierced with the point of a sharp knife, do not allow to over cook as they will fall apart. Different varieties of potatoes need different cooking times.
When the meat has finished cooking put into an ovenproof dish. Cover with the sliced potatoes, making an even covering.
Make the cheese sauce
Melt the butter gently in a saucepan, add the flour and stir into the butter, cook gently for a couple of minutes but do not allow to brown.
Pour in the milk stirring all the time, either with a wooden spoon or a balloon whisk.
Continue to stir until the mixture is smooth, bring to a gentle boil and cook, still stirring, for a couple of minutes.
Remove from the heat and stir in the grated cheese and mustard. Season to taste.
Pour over the potatoes and spread into an even layer.
Bake in the oven at 180 C for approx 1 hour.
Serve with a green salad or peas.