Start by making the chimichurri sauce. Blitz all the ingredients in a food processor until they’re finely chopped but the sauce still has a little texture. Transfer to a bowl and season to taste. The sauce should be punchy, herby and fragrant, with a good kick of chilli. Cover with cling film and put in the fridge to let the flavours develop. Can be made a few days ahead – keep in the fridge until needed.
Take the bavette out of the fridge 1 hr before cooking so it comes up to room temperature. Meanwhile, get your barbecue nice and hot, or heat a large griddle pan until it’s nearly smoking.
Season the bavette liberally with flaky sea salt and a good grinding of black pepper, and rub with oil on both sides. Place on the barbecue or in a griddle pan and cook for 4-5 mins each side or until cooked to your liking.
Rest the bavette for 5 mins, then thinly slice two-thirds of the meat, reserving 500g for the week ahead (see steak with panzanella and curried aubergine with bavette recipes). Taste your chimichurri sauce again and adjust the seasoning if necessary.
Serve with the cheesy corn on the cob and blackened sweet potato mash, and the chimichurri sauce spooned over.