500g/1lb 2oz spinach
1 tsp Dijon mustard
150ml/5fl oz grapeseed oil
salt
1 tbsp apple cider vinegar
20ml/¾fl oz apple cider vinegar
280g/10oz Holstein sirloin or rib-eye steak
50²µ/1¾´Ç³ú bone marrow, soaked in salt water and diced