Scampi, lobster and shrimps cannelonis with cheese sauce

Ingredients

• 2 tablespoons butter
• 2 garlic cloves, finely chopped
• 2 shallots, finely chopped
• 1/2 cup white part leeks, finely chopped
• 2 tablespoons white wine
• Meat from a 454g pack of scampi tails (butterfly open and ready to cook), coarsely chopped
• 1 cup raw shrimps, peeled and tails removed, coarsely chopped
• Meat from 2 lobster tails, coarsely chopped
• Salt and ground pepper
• 1 cup 15% country style cream
• 1/4 cup chicken broth
• 1 cup fresh parmesan, grated
• 1 teaspoon lemon zest
• 475g light ricotta cheese
• Leaves from 3 fresh thyme sprigs
• 8 fresh cannellonis( or more, depending on their size )
• 2 1/2 cups high quality and old gruyese cheese