Roast beef sirloin & béarnaise dauphinoise recipe | Good Food

Ingredients

• 2kg boneless beef sirloin tied
• 2 tbsp olive oil
• ½ tbsp black peppercorns
• ½ tbsp sea salt
• 1 large garlic bulb
• 450g baby carrots halved
• 200g watercress
• 5 tbsp olive oil
• 2 tbsp cider vinegar
• 1 tbsp Dijon mustard
• ½ tsp caster sugar
• 40g unsalted butter plus extra for the dish
• 3 banana shallots finely chopped
• 70ml white wine vinegar
• 500ml double cream
• 500ml whole milk
• 3 large garlic cloves bashed
• small bunch of tarragon leaves finely chopped, stalks reserved
• 1 large egg yolk (freeze the white for another recipe)
• 1½ kg Maris Piper potatoes thinly sliced
• 70g gruyère grated