Preheat the oven to 180 degrees Celsius or 350 degrees Fahrenheit.
Lay the nuts on a baking tray and roast for 8 to 10 minutes, shaking occasionally. Set aside to cool.
Blitz the remaining ingredients in a food processor until smooth, adding more oil to loosen if necessary. Roughly chop the nuts and add to the salsa, season to taste and set aside.
Drain the beans and heat in a saucepan with the butter and cream for 5 minutes until the beans are soft. Pour into a food processor and blend until smooth. Season to taste with salt and white pepper then return to the pan and keep warm until needed.
Heat a barbecue or griddle pan to a high heat. Season the steaks with plenty of salt and pepper then cook for 2 to 3 minutes on each side.
Transfer to a board to rest for 5 minutes, slice thinly then pour the resting juices into the salsa verde. Serve the steak with the bean mash and salsa verde.