2 slices rye or pumpernickel bread
1 T. unsalted butter, softened
1 to 2 tsp. Dijon mustard
2 slices (1 ounce each) Muenster cheese
1/4 of a firm ripe avocado, peeled, pitted, thinly sliced
3 ounces sliced turkey

Spread butter on one side of each bread slice. Spread mustard on other side of bread slices. On top of mustard, layer Muenster, avocado, and turkey. Season with salt and pepper if desired. Top with remaining slice of bread, buttered side up.

Heat a heavy skillet and cook sandwich until toasted and cheese is melted, about 2 minutes per side. Serves 1.