想請問如果我想要求餐廳在上甜品時，在甜點旁邊寫上happy birthday 英文應該點寫或點講呢？唔該?

Would you please write “happy birthday “ with chocolate or anything on the plate of the dessert, please?

Easy, just say:

Could you write "Happy Birthday to Princess" on the dessert (cake, or whatsoever) we just ordered?

Could I (siu ching) ask for expressing praise, given free out of courtesy kindness="complimentary";the dessert served with the writing "Happy Birthday",on my behalf,from your Restaurant, please?
ie:-Add "Happy Birthday" to the Cake for the bill.

Would you be kindly enough to put the congratulation words of "Happy birthday" aside of that dessert. Yip

Would you please place a card with words "Happy birthday" by the dessert that you will serve to us?