Instructions

1. Flank is a lean, coarse-grained cut and it wants trimming before anything else. Run a knife under every silver seam and every yellow fleck of fat: fat will not dry, and a strip carrying a seam goes rancid weeks ahead of the rest of the batch.
2. Put the trimmed steak in the freezer until the outside is firm and the middle still gives. Half-frozen beef holds still under the blade; soft beef rolls away from it and you end up with strips of six different thicknesses that finish at six different times.
3. Cut across the grain at 6 mm, keeping the slices as even as you can manage. Across the grain gives a jerky that breaks apart in the mouth rather than one you have to worry at.
4. Seed and chop the jalapenos, then warm them with the soy, Worcestershire and liquid smoke until everything has come together. Chilli heat is oil-soluble and sits in the seeds and the white ribs, so seeding them is what keeps this on the right side of edible.
5. Cool the marinade before it meets the meat and only then pour it over. Warm marinade starts cooking the surface of the beef, which seals it against taking any flavour in.
6. Leave it covered in the fridge for a full day, turning the container over once along the way. The steak is ready when no red remains in the centre of a cut strip.
7. Lift the strips out, let them drain, and lay them across the trays without letting any two touch. Anywhere they overlap stays wet and pale.
8. Dehydrate at 71 °C for 7 hours. The setting is high because raw beef is going in, so leave it where it is.
9. Finished jerky folds without breaking and shows no pink at all in the fold. Let a strip come down to room temperature before it goes in a jar — sealed warm, the batch steams itself soft.