Mix marinade ingredients with 30ml of water in a bowl.
Coat meat in marinade and refrigerate for four hours.
Rinse potato chips under cold water and pat dry.
Heat sunflower oil to 130°C and fry potatoes for 10 minutes until soft.
Drain potatoes on kitchen paper and set aside.
Reheat oil to 190°C and fry chips for 5 minutes until crisp.
Drain chips, season with salt, and keep warm.
Drain meat and reserve the marinade for later.
Heat vegetable oil in a wok until smoking and brown the meat quickly.
Stir in onion wedges and cook for one minute.
Add tomato, chilli, and pisco to the wok.
Pour in reserved marinade and bring to a simmer.
Rest meat in the sauce for two minutes off the heat.
Serve steak and chips garnished with herbs.