The great big Observer Food Monthly Christmas leftovers sandwich

The bread
We make focaccia at the sarnie shop, but use anything you like. I think sourdough is much too chewy and the air-holes far too big to be any use in a decent sandwich, but each to their own. I suggest a tranche of focaccia 6cm high, 9cm wide and 14cm long.

The turkey
Chop up 150g of leftover turkey, put it in a pan, cover it in gravy, add a splash of water and set it aside.

Mayonnaise
The only thing you can get wrong when it comes to this sandwich is not making it big enough

Plonk two heaped tablespoons of mayo into a bowl, add 2 flat tablespoons of leftover gravy and 1 teaspoon of your favourite condiment. Anything, mustard, cranberry, horseradish. Stir it until completely integrated, set aside.

Add some crunch
Hopefully you’ll have leftover raw sprouts (5 or 6), carrots (1-1½ will do), some kind of lettuce (½ a baby gem) and a load of parsley (a big handful). Whatever you’ve got, go really thin (ie veg peeler) or grated on harder stuff and don’t be too tough on the softer stuff (rip, don’t cut). Put your veg in a bowl, and mix up a vinaigrette to put on it later: 1 tablespoon of acid (lemon juice or vinegar) to 2 tablespoons of oil (nice rapeseed or olive oil) and a “two finger one thumb” pinch of salt. Ideally, stick it all in a jam jar or something with a lid so you can shake it to emulsify.

Use up those vegetables
Take your leftover roasties, bread sauce, cooked veg and stuffing and mash them in a bowl with a fork. Add more pepper, more salt and a nice squeeze of lemon juice. A bit more of your condiment of choice if you so choose. Then crack an egg into it. Mash. Mash. Mash. Use your hands to squeeze them into little patties and get the egg properly incorporated. If you have the time, half an hour in the fridge will help them hold together when you fry them. Make them roughly half the size of your sandwich so the knife can go between them when you cut the sandwich in half later. And don’t make them too thin. You want soft inside, crunchy outside, post-frying.

Crisps (seriously)
Procure either (or perhaps both) a bag of pork scratchings or some ready salted from the pub. Give the scratchings a go with a wooden mallet or a rolling pin, still in the bag, to break them into little teeny chunks. If you’ve got crisps, open the bag and give them a few crushes with your hand.