Cook the pasta according to the pack instructions. Drain. Meanwhile, melt the butter in a saucepan. Stir in the flour and cook for 1 minute. Gradually blend in the milk. Bring to the boil, stirring until thickened. Stir in the Garlic Italian Seasoning, Nutmeg, mustard, vegetables and tuna. Season. Cook for 2-3 minutes. Stir in the cooked pasta, heat through and transfer to a heat-proof serving dish. Top with cheese and place under a pre-heated grill until golden.