A few tweaks transform the old-school grilled ham and cheese.
Blanch broccoli rabe in batches in a pot of salted boiling water until just tender, about 2 minutes. Drain.
Heat oil in a large skillet over medium heat. Add garlic; cook, stirring, 30 seconds. Add broccoli rabe; cook, stirring, 2 minutes. Season with salt. Let cool slightly, then finely chop.
For each sandwich, spread 2 teaspoons jam on one bread slice and 1 teaspoon mustard on another. Layer one slice with cheese, broccoli rabe, and ham, dividing evenly. Close sandwich; brush each side with butter.
Heat a large cast-iron skillet over medium heat. Cook sandwiches in batches until golden brown, flipping once, about 3 minutes a side. Serve immediately.