Beef fillet with a gratin of mushrooms (gordon ramsay)

Ingredients

• Beef Fillet
• • 1 shallot, finely chopped
• • 1 garlic clove, crushed
• • 4 tbsp olive oil
• • 100g mixed mushrooms (shiitake, oyster), roughly chopped
• • 100g chestnut mushrooms, roughly chopped
• • 2 tbsp chives, finely chopped
• • 4 tbsp double cream
• • 1 large egg yolk
• • 4 fillet steaks, about 180g and 4cm thick
• • 3 tbsp freshly grated Parmesan
• New potatoes
• • 500g new potatoes, scrubbed
• • 5-6 tbsp olive oil
• • Few sprigs of rosemary
• • 8 garlic cloves, skin on and lightly crushed
• • Knob of butter
• • Sea salt and freshly ground black pepper