Seafood Gratin

Ingredients

• For the sauce
• 250ml seafood stock or clam juice
• 250ml double cream
• 125ml good white wine, such as Chablis, plus 3 tbsp
• 3 tbsp tomato puree
• 1/2 tsp saffron threads
• 225g raw prawns, peeled, deveined, and cut in half crosswise
• 225g raw halibut, cut into 2.5cm chunks
• 225g cooked lobster meat, cut into 2.5cm chunks
• 105g unsalted butter, divided
• 1 tbsp plain flour
• Salt
• Freshly ground black pepper
• 300g julienned leeks, white and light green parts
• 3 julienned carrots
• 100g panko (Japanese dried bread crumbs)
• 35g freshly grated Parmesan
• 20g minced fresh flat-leaf parsley
• 15g chopped fresh tarragon leaves
• 2 cloves garlic, minced