The key to making a great bacon sarnie, according to Fergus Henderson, who should know a thing or two on the subject, is simplicity. If the essentials – buttery toast, bacon, lashings of tomato ketchup – are of sufficiently high quality, why complicate matters with extra ingredients? "HP sauce is fine," he says, "but mustard adds the wrong kind of sharpness, and oddities like marmalade are a step too far. Same with fillings: tomato and lettuce are all good, but not at breakfast. Avocado is a bit racy. My wife, who is from New Zealand, would go there, but not me. Bacon and fried egg in a sandwich? That's too much."

We are in the dining room at the St John Hotel in central London, the latest Henderson temple to great British food, and the man himself is at the kitchen counter overseeing the production of one of their most popular breakfast indulgences. "Everyone loves a bacon sandwich," he says as it is laid down before us on a white plate with a jar of ketchup on the side. "The smell, the taste… it's a sensuous thing." We divide the sensuous thing between us and eat. A long moment passes before either of us speaks again. It is, quite simply, the best bacon sandwich I've ever had.

The bread

We use a simple white sandwich loaf from the St John bakery, sliced not too thick. The bread needs to be toasted, to give the sandwich some rigour.

A normal toaster will suffice, but we use an open grill which gives the bread a nice singe – singe is definitely a good thing. In a perfect world, you might even pan-fry the bread in some pork dripping.

The bacon

The bacon we serve comes from a farm in Gloucester and we've started curing it ourselves at the hotel.

Bacon from the shoulder is my favourite, unsmoked and lightly cured. It goes on the grill alongside the bread – four slices per sandwich – or under your oven grill at home. The degree of crispiness of the bacon is up to you.

The butter

Butter is important – it lubricates the sandwich and makes it easier to eat – so butter both slices of bread liberally and lay out the bacon between them.

Serve the sandwich with ketchup on the side. We make our own. It's just tomato, onions, vinegar, apples and various spices – no mysterious monkish element prepared late at night. [The recipe can be found in the first St John cookbook, Nose to Tail Eating].

As for an accompanying drink, you know what's good? A glass of chilled Breton cider goes very well indeed with a bacon sandwich. Bon appetit!