Perfect roast beef sandwich

I've had such a craving lately for roast beef sandwiches. This is my idea of the perfect combination of flavors for a roast beef sandwich.

Perfect Roast Beef Sandwich
2 half-inch slices toasted sourdough pugliese bread
2 Tbsp dijon-horseradish sauce (see below)
3-4 slices thin, rare roast beef
1 thin slice sharp cheddar cheese
1 leaf butter lettuce

Spread the both slices of toasted bread with the mustard sauce, then top with the meat, cheese and lettuce. Enjoy!

Dijon-Horseradish Sauce
2 Tbsp lowfat sour cream
2 Tbsp dijon mustard
2 tsp prepared horseradish
salt & pepper

Mix the first three ingredients together in a small bowl, and add salt & pepper to taste. Makes enough for 2-3 sandwiches.