This Seeking Tech guide will show you how to easily kill the chef as Grace in Resident Evil Requiem.
While you can try to take him on normally, you have to waste a lot of precious ammo. To see how you can fight him with guns only, you can check out the video below:
To kill him efficiently, you should use the Hemolytic Injector. You should find one in the Examination Room at the East Wing. You can also craft some when you find the Blood Collector at the Blood Lab.
Once you have the Hemolytic Injector, sneak up behind the chef and inject him. He should die instantly and drop the pantry key, which houses a lot of great items. Check out the video below to see how this is done: