Grilled Roast Beef Sandwiches

4 Tbsp. horseradish mustard
3/4 c. sauerkraut, drained
8 slices focaccia-style bread
1/2 lb. sliced roast beef
8 slices Muenster cheese

Spread 1/2 tablespoon mustard on each slice of bread. Arrange roast beef, sauerkraut and cheese on four slices bread, dividing evenly. Cover each with second slice of bread, mustard side down. Grill sandwiches over medium heat until cheese melts slightly, turning sandwiches over once and pressing down firmly with metal spatula. Cut in half to serve. Makes four servings.