I like this list because it’s full of things that one might be tempted to say thinking one is saying something good. This advice comes from the Sugoren Japanese online dating and information site.
1. “Surprisingly, it tastes normal.”
2. “I’m not really that hungry you know.”
3. “You should let my mother teach you.”
4. “Is this all?” (kind of implying that there isn’t enough, or not enough selection… note: Japanese home cooked meals often consist of a lot of different little dishes)
5. “It’s not bad, but I think it’s missing a little something…”
6. “That’s not the way it’s usually made, right?”
7. “2 stars!” (Acting like a gourmet or Michelin with an scale that’s not clearly defined)
8. “Can I add a little flavor?” (taking it upon yourself to “fix” it)
9. “…” (saying nothing at all)
We are advised, then, to be polite and show your thanks with your comments.
Personally, I think that you can go a long way in praising the effort someone made in cooking, and leave the negative comments for when the relationship is in that place. This applies to your upcoming home-cooked Christmas dinner as well as the chocolates you are going to get in a month and a half.