BBC Food - Recipes - Lobster with garlic butter, new potatoes and watercress salad

Ingredients

• 3 tbsp sea salt
• 1 sprig thyme
• 6 white pepper corns
• 1 bay leaf
• 1 lemon
• 4 x 450g/1lb live lobsters
• 50g/1¾oz butter
• 450g/1lb new potatoes
• salt
• freshly ground black pepper
• 1 tsp English mustard
• 2 tbsp white wine vinegar
• 4 tbsp olive oil
• 4 tbsp vegetable oil
• 4 little gem lettuce , washed and halved
• 1 large bunch watercress , washed
• 225g/8oz butter
• 1 shallot , finely chopped
• 4 garlic cloves, crushed
• 12 cooked whelks , chopped into small dice
• 6 tbsp parsley , chopped