Heat the oil in a large saucepan over medium heat. Add the reserved prawn heads and shells, and cook, stirring, for 4-5 minutes or until the shells are browned (the shells will pop and crackle loudly).
Add the onion, carrot, celery, garlic and bay leaf, and cook, stirring often, for 5 minutes or until the onion is soft.
Discard the prawn heads. Add the water, wine, rice, tomato paste and saffron to the pan, and bring to the boil over medium-high heat. Reduce heat to medium-low and simmer, uncovered, for 15 minutes or until the rice and vegetables are tender. Set aside to cool for 10 minutes.
Transfer the mixture to a blender (shells included) and blend until very smooth. Strain through a coarse sieve into a clean saucepan. Stir in the extra water. Taste and season with salt and pepper.
To make the garlic baguette, preheat grill on medium-high. Combine the Dairy Soft, garlic, salt and pepper in a small bowl. Spread the mixture thinly over the baguette slices. Place slices on a baking tray and cook under preheated grill for 2-3 minutes or until golden.
Meanwhile, bring bisque to a simmer over medium heat and add prawns, scallops and salmon pieces. Cook, uncovered, for 3-4 minutes or until seafood is just cooked. Ladle into serving bowls, sprinkle with the thyme leaves and serve immediately accompanied by the garlic baguette.