1kg/2lb 4oz floury potatoes, such as Maris Piper, peeled and cut into chunks
1 garlic clove, peeled and finely chopped
2 tbsp chopped flatleaf fresh parsley leaves
4 banana shallots, 2 with skin on and cut in half lengthways, 2 peeled and finely chopped
2 tbsp finely chopped fresh tarragon leaves
175ml/6fl oz veal stock (or chicken stock if not available)
sea salt and freshly ground black pepper
25g/1oz caster sugar
1 tbsp olive oil
225g/8oz unsalted butter
150ml/5fl oz double cream
4 x 250g/9oz sirloin steaks, at room temperature
250ml/9fl oz red wine