1. In a frying-pan, heat 1 tbsp vegetable oil and fry the chicken and then cauliflower. Cook for about 5 min or until chicken is slightly browned. Stir frequently to prevent burning. Add salt to season. Transfer to a baking dish. Set aside.
2. Making the sauce In a medium saucepan, heat the mayonnaise over medium-low heat until melted. Stir in the flour. Gradually pour the milk into the mixture, stirring continuously until the sauce has thickened. Add ingredient "A" to season.
3. Pre-heat the oven to 200℃.
4. Pour the sauce onto the chicken and cauliflower. Sprinkle the grated cheese onto the sauce.
5. Bake the gratin for about 40 mins or until browned.