1. Finely chop the onions and shallots, set aside.
2. Clean and wash the all the seafood, set aside.
3. In a saucepan add the butter, and melt it over low heat, add shifted flour and prepare the roux, once the flour is cooked gradually add the milk and stir, continue until you get a creamy sauce.
4. Add the onions, salt, garlic paste; continue to stir until everything it well combined.
5. Add seafood seasoning followed by the shallots, stir and combine everything.
6. Remove from the heat and set aside.
7. In a frying pan pour oil and sauté the calamari on low heat, add the scallops, salmon and prawns, keep stirring everything.
8. Add garlic paste and water, stir and cook the seafood completely.
9. Once done drain the excess water in a bowl.
10. Place the mornay sauce back on heat and add the reserved seafood water and stir the sauce.
11. In a serving bowl put one layer of seafood followed by the mornay sauce, continue the same step to you desired amount.
12. Sprinkle shredded cheese on top and place it in the microwave for 3-4 minutes or in the oven at 180 degree for 5-6 minutes, for the cheese to melt.
13. Serve the seafood mornay hot along with a French bread.