3 Tbs. apple butter
1 tsp. Dijon mustard
1/2 tsp. honey
4 1/2-inch-thick slices sourdough bread
8 oz. aged white Cheddar,thinly sliced or coarsely grated (about 2 cups)
2 oz. thinly sliced pastrami
6 to 10 very thin slices of apple, preferably honey crisp
1-1/2 oz. (3 Tbs.) unsalted butter
Combine the apple butter, mustard, honey, and a good pinch of kosher salt in a small bowl. Spread evenly on two slices of bread and top with half of the cheese and the pastrami. Top that with a layer of sliced apple, overlapping the slices slightly, and the remaining cheese. Top with the other slices of bread to make two sandwiches.
Melt 2 Tbs. of the butter in a heavy-duty 12-inch skillet over medium-low heat until lightly browned. Add the sandwiches and cook, adjusting the heat as necessary, until golden brown on one side, 3 to 4 minutes. Flip, add the remaining 1 Tbs. butter, and cook, lifting the edges of the bread to allow the butter to run under and adjusting the heat as necessary, until the cheese has melted and the other side is golden brown, another 3 to 4 minutes. Slice in half and serve.