Ultimate Roast Beef Sandwich

• 2 ounces unsalted butter, softened
• 4 slices of crusty white bread
• 2 tablespoons English mustard
• 8 ounces roast beef, thinly cut
• watercress, to serve
• 23 cup heavy cream, lightly whipped
• 23 cup mayonnaise
• 6 tablespoons horseradish, freshly grated
• 2 tablespoons English mustard
• 1 dash Worcestershire sauce
• 1 tablespoon lemon juice
• 1 pinch sugar
• salt & freshly ground black pepper
• 12 ounce unsalted butter
• 2 leeks, washed and thinly sliced
• 2 tablespoons muscovado sugar
• 2 tablespoons dry white wine
• 2 ounces butter
• 2 potatoes, cubed

1. To make the horseradish sauce, combine the cream, mayonnaise, horseradish, mustard, Worcestershire sauce, lemon juice and sugar.
2. Season to taste with salt and freshly ground black pepper and then set aside.
3. Melt the butter over a medium heat in a frying pan.
4. Add the leek and cook for 8-10 minutes until wilted.
5. Add sugar and wine and cook gently for 20 minutes until the leeks have caramelised.
6. For the potatoes, melt the butter in a frying pan and fry the potatoes until soft and golden.
7. Meanwhile butter one side of each piece of bread and season.
8. Fry the bread, on the buttered side for 1 minute and dust with pepper.
9. Spread mustard on the soft, unbuttered side of the bread and reserve.
10. To assemble the sandwiches, layer the potatoes, leeks, horseradish and roast beef on the toasted bread, top with bread to form a sandwich, cut diagonally, secure with a toothpick and serve with watercress.

unsalted butter, crusty white bread, english mustard, beef, heavy cream, mayonnaise, horseradish, english mustard, worcestershire sauce, lemon juice, sugar, salt, butter, leeks, muscovado sugar, white wine, butter, potatoes

Taken from www.food.com/recipe/ultimate-roast-beef-sandwich-231252 (may not work)