Crispy stuffed mushrooms

INGREDIENTS

• 2 large, flat mushrooms (such as Portabello or field mushrooms
• 100g/3½oz Chinese mushrooms
• 1 garlic
• 1 tbsp melted butter
• 1 large free-range egg
• 2 tbsp white breadcrumbs
• 2 tsp chopped chives
• 2 tsp chopped parsley
• 1 tsp chopped thyme
• salt and freshly ground black pepper
• pinch freshly ground nutmeg
• 200ml/7fl oz whole milk
• few slices of carrot
• few slices of onion
• 2 peppercorns
• sprig thyme
• sprig parsley
• 15g/½oz plain flour
• 15g/½oz butter
• 1/8 teaspoon mustard
• 15g/½oz cheddar
• 15g/½oz parmesan
• 25g/1oz butter
• 50g/1¾oz soft white breadcrumbs
• 40g/1½oz grated cheddar cheese, or 25g/1oz grated parmesan cheese