Back to sandwiches for a moment…
If you really want to up your game on sandwiches and related dishes, try experimenting with the cheeses you use.
For instance, I’ve tried many different kinds on my ham sandwiches, and one unlikely pairing I found worked well was blue cheese. Use a good one- Stilton, blue castello, cambozolla- and the tangy cheese will play nicely with the salty ham.
Or consider the classic lox & cream cheese on a bagel. I subbed a garlic herbed D’affinois (a kind of Brie) for the cream cheese and was rewarded with a more complex and tasty dining experience. I bet a gournay (see Boursin) would also make for a nice change up.
And then there’s the simple perfection of a grilled cheese/ham & cheese. For most of my life, I made them either with American cheese or velveeta. But I’ve experimented with goudas, gruyères, havartis and others, and now it’s unusual for me to use fewer than 3 different cheeses simultaneously when I make one.
Beyond that? There’s a big world of breads, mustards, sprouts, herbs and so forth to experience.