Havarti pairs well with asparagus, while Parmesan adds just a bit of a salty kick and Dijon a little tang that takes these sandwiches up another notch!
Preheat the oven to 400 degrees and spread trimmed asparagus out on a rimmed baking sheet. Drizzle with olive oil and toss to coat, then season with sea salt and black pepper.
Roast at 400 degrees for 10 minutes, or until slightly browned and crisp-tender.
While asparagus is roasting, butter all eight slices of bread.
When the asparagus is done, it's time to make your sandwiches. You should be able to cook two at a time in a large skillet, so will have to make yours in a couple of batches in order to feed four.
To assemble the asparagus grilled cheese sandwiches:
Turn the heat to medium under a large skillet
Place two slices of bread butter side down in the skillet.
Spread each slice with a thin layer of Dijon mustard.
Add a slice of Havarti, tearing into pieces to fit the bread.
Top with roasted asparagus spears.
Add a second slice of Havarti, again tearing into pieces to fit.
Sprinkle with a little shredded Parmesan.
Top with a second slice of bread, butter side up.
Cook for about six minutes over medium heat, or until the bottoms of your sandwiches are nicely browned.
Flip carefully (I like to use a wide pancake turner for this maneuver), then cook for another 5-6 minutes, or until both sides are browned and cheese is nicely melted.
Repeat the process with your second batch of two sandwiches, then serve!
Notes
Thinner asparagus spears will work better for sandwiches, but roast more quickly; if your asparagus stalks are thicker they may need a little more time in the oven. You can save time by pre-roasting the asparagus the night before, too, so that you just need to assemble and cook up the grilled cheese sandwiches the next day (or use leftover roasted asparagus for these!) I actually roasted up a whole pound of asparagus here since mine was pre-packaged that way -- this was more than we needed for sandwiches, but then you can enjoy the surplus on the side.