I’ve used minced beef here, but minced pork would also be delicious, as would a mixture of the two.
My wife doesn’t like onions, so I’ve used leeks here, but by all means use white or red onions, or even use shallots or spring onions.
The lentils are optional, but they’re great for upping your veg count. Feel free to swap in drained tinned beans instead – just scrunch them with clean hands first to break them up a bit.
When it comes to herbs for your burgers, any soft ones will be delicious; parsley, mint, marjoram, chervil, tarragon, or you could even use rosemary or thyme.
For the salsa, it’s fine to use tinned or frozen sweetcorn, and you could swap in jarred peppers if you don’t have fresh. Carrot or cucumber would add a nice bit of crunch, and the pineapple could be tinned, or it could be peach, apple or pear. You need acidity for the salsa, so vinegar, lemon or lime juice are all good, or use a mixture.