Separate two eggs, placing yolks in a medium saucepan and reserving egg whites in a small bowl covered in refrigerator until required.
Add remaining 2 eggs, carob syrup, cream, milk, carob powder, spices and vanilla to the saucepan with yolks, stirring to combine. Place over a medium-low heat, stirring continuously until mixture thickens slightly and coats the back of a wooden spoon. Remove from heat, add brandy stirring to combine. Place in refrigerator overnight to chill or for up to three days.
To serve, whisk reserved egg whites to a soft peak. Add to eggnog, folding gently to combine. Pour into glasses and sprinkle tops with extra carob powder.