|Polyunsaturated vegetable margarine/Butter||1⁄2 Ounce (3 Tablespoon Or 40 Gram)|
|Flour||1 1⁄2 Ounce (1/3 Cup Or 40 Gram)|
|Milk||1⁄2 Pint (1 1/4 Cups Or 300 Milliliter)|
|Edam cheese||2 Ounce, grated (1/2 Cup Or 50 Gram)|
|Mustard||2 Teaspoon (10 Milliliter)|
|Water||30 Milliliter (2 Tablespoon)|
First make the sauce. Put the margarine or butter in a bowl and cook for 1 minute. Stir in the flour. Pour on the milk. Cook for 3 minutes, whisking after each minute. Stir in the cheese and mustard, if used. Cook for a further minute and whisk again. Season to taste with salt and pepper. Keep the sauce warm while you cook the leeks.
Trim the leeks and wash thoroughly. Put them in a dish with the water, cover with vented cling wrap (plastic wrap) and cook for about 8 minutes, rearranging once, until done.
Drain the leeks and cut off a few rings for the garnish. Wrap each in a slice of ham, lay side by side in the dish and pour the sauce over. Cover and cook for 2 - 3 minutes until hot through.
Garnish with leek rings.