Strictly speaking this BLT is an BRT, R being for Rocket which may or may not be actual lettuce. It's certainly got green leaves and is found in the salad aisle but who knows? Is this the greatest sandwich of all time ... not sure. Here are a few other contenders:
Crayfish and rocket. Pret did a good version of this if you're too posh to DIY.
A piece (or a sandwich) on real chips with brown sauce. Once a food staple. Not sure of it's current status, it may have died along with the once ubiquitous chip pan.
Peanut butter and jam - has to be strawberry jam and crunchy peanut butter. Smucker's Goober (which is actually grape) is a good alternative if you can find it.
Pastrami and pickle (NY Deli style), possibly with some slices of American cheese somewhere in there.
Crisps (any flavour but vinegar) but with a generous amount of mayo added for lubrication.
Anchovies and mustard in/on toasted bread. Maybe a slice of tomato on top? A bit left field for those of you with more Presbyterian tastes and outlooks, but this can work.
I was going to add fish fingers but I'm exhausted now.
As for the bread it used to be the old Scottish plain loaf that was the best, it was the default, certainly for chips. The plain loaf seems to have been cancelled for health reasons or perhaps it's just another part of Scottish counter culture that has been outlawed by our unseen lords and masters. I can no longer find it in the markets and it's now taken to be obsolete. A strange relic from the past, like scarlet fever or corporal punishment.
These days it's sourdough (white) that's everywhere and I seem to have got myself stuck in that particular and for the mean time fashionable rut. At £2.50 for about seven slices, all full of air bubbles, it's hardly priced as a basic food. It is good bread. In fairness the other, cheaper breads can be pretty grim and tasteless, though rye can be a wee treat if you can get a good loaf. Very dense.
Please note that bread rolls, stotties, English breakfast muffins, brioche buns or whatever you call them are not included in this mild but biased opinion piece because they cannot be considered as the basic and foundational ingredient of a proper sandwich.

.png)

.png)

.webp)
