Chateaubriand with a bone marrow sauce

By Matt Tebbutt From Saturday Kitchen Ingredients For the crisp shallots 2 banana shallots, unpeeled 4 thyme sprigs 12 tbsp olive oil For the chateaubriand 1 chateaubriand steak dash oil 1 head of garlic, halved few thyme sprigs 50ml/2fl oz Madeira wine 30g/1oz butter salt and freshly ground black …