Based on the level of respect or formality, you can say "What would you recommend on the menu?" in Korean in 3 ways:

• Informal: neo-neun menyu-eseo mwol chucheon-hani? (너는 메뉴에서 뭘 추천하니?)
• Formal: dangsin-eun menyu-eseo mwol chucheon-hanayo? (단신은 메뉴에서 뭘 추천하나요?), dangsin-eun menyu-eseo mwol chucheon-hapnigga? (당신은 메뉴에서 뭘 추천하십니까?)
• Very Formal: dansin-ggeseo-neun menyu-eseo mueot-eul chucheon-hasipnigga? (당신께서는 메뉴에서 무엇을 추천 하십니까?)

- what (objective): mwol (무얼), mueot-eul (무엇을), mwo-reul (뭐를)
- you (subjective): neo-neun (너는), dangsin-eun (당신은), dansin-ggeseo-neun (당신께서는), ne-ga (네가), ni-ga (니가)
- to recommend: chucheon-hada (추천하다)
- menu: menyu (메뉴), sikdanpyo (식단표)

Please refer to How to pronounce Korean Alphabet for the English pronunciation in this answer.