- In a large casserole pan (a 9 by 13 will make all but 2 of your manicotti noodles), lay out your manicotti noodles. Pour boiling water over them until they are covered. Let soak 30 minutes. Drain off and let the noodles cool. 
- Mix the seafood, egg, onion, mozzarella cheese, Old Bay seasoning, mayo, and the 2 tablespoons of milk together.  
- Stuff the seafood filling into the cooled manicotti. To make this easier, use a Ziplock bag with a corner cut off.  
- In a medium heavy saucepan, melt the butter on low/medium heat. 
- When the butter is melted add the cornstarch and whisk just until smooth.  
- Add the minced garlic and whisk gently for about 1 minute or until fragrant. 
- Slowly pour in the milk, whisking continuously. Heat until the sauce thickens up a bit. Do NOT boil. 
- Add the parmesan cheese, return the pan to the heat, and continue stirring until the cheese is melted and the sauce is smooth.  
- Add the salt & pepper. Taste and add additional salt & pepper, if needed. 
- Spread the ricotta over the stuffed manicotti and top with the sauce. NOTE: if you are making a 9 by 13 pan you most likely won't use about 1/2 cup of the sauce.  
- Put into 350 degree preheated oven and bake for 45 minutes or until hot and bubbly. 
- Remove from the oven, turn the oven to broil. Top with parsley and broil for about 5 minutes or until golden brown. 
- Let cool before serving. Serve with a squeeze of lemon and sprinkle of fresh parsley.