Cottage Pie

For the filling

40g butter

2 tbsp olive oil

400g minced beef

1 large onion, diced

3 carrots, peeled and diced

2 celery sticks, diced

2 cloves garlic, minced

1 beef stock cube

2 tbsp plain flour

1 x 400g tin chopped tomatoes

400ml chicken stock

2 tbsp tomato purée

2 tbsp chopped parsley

1 tbsp thyme

2 bay leaves

Salt and pepper, to taste

For the topping

1.5kg potatoes, peeled and halved

200ml milk

100g butter

100g white cheddar cheese, grated

Salt and pepper, to taste