|Potatoes||6 Pound, peeled and roughly chopped (2.75 kilogram)|
|Butter/Margarine||5 Ounce (150 gram)|
|Freshly ground black pepper||To Taste|
|Flour||1 Ounce (25 gram)|
|Milk||6 Fluid Ounce, warmed (175 milliliter)|
|Soured cream||1⁄4 Pint (150 milliliter)|
|Freshly grated nutmeg||1 Teaspoon|
|Leeks||2 , trimmed, thinly sliced, blanched and drained|
|Stale white breadcrumbs||4 Ounce (100 gram)|
Preheat the oven to Gas 5, 375°F, 190°C, 10 mins before cooking.
Place potatoes in a pan of boiling water and cook for 15-20 mins.
Drain, then mash with 4 oz/100 g fat.
Season and stir in 1/2 oz/15 g flour.
Sprinkle remaining flour over potato, cover and leave to stand overnight.
Stir in milk and soured cream, then beat until mixture forms a smooth paste.
Adjust seasoning, then add nutmeg and blanched leeks.
Place in a 4 pint/2.25 litre casserole.
Sprinkle breadcrumbs over top of potato and dot with remaining butter.
Bake for 40 mins, or until crisp and golden.