Here are 2 great sandwiches that I love to make. These are serves at the Foundry on Melrose Ave in LA. Chef there is Eric Greenspan. I reduced the butter in these.
Johnny Apple Cheese, a.k.a. Johnny Pastrami
. Makes 4 sandwiches
Ingredients:
1/2 pound butter, 1/2 cup mustard seeds
,5 Granny Smith apples, cored and sliced thin
1y, medium onion, sliced thin
, 2 tablespoons Dijon mustard,
 2 tablespoons honey,
1/2 cup apple cider
, 1/2 cup cider vinegar, 
8 slices of extra sour sourdough bread, 16 slices aged white Cheddar, 
1 pound pastrami, sliced thin.
1. For the apple mustard chutney: In a pan over medium heat, heat two tablespoons of butter until it foams. Add the mustard seeds and toast in the pan for 1 minute, and then add most of the apples (reserve 8 slices) and onions and cook until tender. Add honey, cider, vinegar and Dijon mustard, and reduce until the liquid is absorbed. Take off heat and puree in a blender until mostly smooth.
In a large pan (cast iron is best) or griddle, melt half of the remaining butter and 4 slices of bread. Top each slice of bread with 2 slices of cheddar cheese and toast until golden brown. When the cheese is melted, add 1/4 of the pastrami to each slice, a dollop of chutney, and two thin slices of raw green apple. Cover with remaining bread. Add remaining butter, flip sandwich and grill until other side is equally golden brown. Cut each sandwich in half and serve hot, preferably with a frilly toothpick.
The Champ: Grilled Taleggio Sandwich With Apricots and Capers. 
Makes 4 sandwiches.
Ingredients:
15 dried apricots
1 tablespoon nonpareil capers
1 tablespoon Dijon mustard
1 tablespoon extra virgin olive oil
8 slices dark raisin bread
5 tablespoons butter, at room temperature
4 small handfuls arugula
8 ounces taleggio cheese, rind removed, at room temperature
4 pinches fleur de sel
1. Place apricots in small saucepan and add water just to cover. Bring to full boil and immediately remove from heat. Mix in capers, mustard and olive oil. Pulse in blender to chunky consistency; set aside.
2. Spread one side of each bread slice evenly (to the edges) with 1/2 tablespoon butter. With buttered sides down, top four slices with 2 tablespoons of apricot mixture, handful of arugula and equal portions of cheese. Top with remaining slices, buttered side up.
3. Place large skillet over high heat, and melt remaining 1 tablespoon butter. Reduce heat to low and add sandwiches. Cook until browned and crisp on both sides, about 2 minutes a side. Transfer to a platter lined with paper towels, and sprinkle each with a pinch of fleur de sel. Cut in half and serve.
Chef Greenspan sometimes serves the cheese sandwich with a layer of braised beef. I have not been able to find that recipe.
Sorry for the stuff that came up in the ingredient list. I was adding commas and got this crazy stuff instead.