Austere can have a meaning like unadorned or plain, so I wonder if that's what it means here. Octopus is a less distinct flavour than prawns, so I guess you could say that means it's plain... It is a strange word to use in this context though! I've never heard austere applied to food (or wine!) before. I would use it about a person, for example, who was particularly cold and unapproachable, or a style of art/design that was quite spartan and simple.

You know? I think when the writer says “austere” they mean “subtle” Which means not such a strong flavor. Austere has a rather different meaning and probably would not be used to talk about food. I hope that helps 🙏