"Him: Trying to find something for supper. (He pulls out frozen beef and says "oh I can't cook that because it's frozen" and then puts it back in the frig. and goes to find something else to cook)
Me: Oh, I cook beef from it's frozen state quite often. Not a problem. (I say this as calm and non-threatening as possible.. not at all meant as telling him what to do. Just simple conversation - I thought).
Him: Sounding annoyed, he says I know. I'll find something else."
Sigh... I know. You're answering him the way you would a friend, etc. But chances are, he takes it as if you're (subtly) trying to tell him what to do. You're his mum, and he may see it that way, no matter how you phrase it. Perhaps a better reply would be, "Oh. Well, hope you find something else" or "Oh, well I'm sure you'll find something else." Then maybe you'll get a non-annoyed, "Yes, I will."
Or maybe even just say, "Ok, I'll leave you to it. Just wanted to say hello and that I love you." Then perhaps you'll just get a "Love you, too, Mum" back and end the conversation happily.
I'm not trying to tell you what to say, just making suggestions. My point is, it might be better not to comment on what your DSs are doing, at all, since they seem to take it the wrong way. If they end up feeling annoyed w/ these conversations, they're less likely to want to have them. If the conversations are comfortable, then, perhaps they'll be more likely to respond. Or not. But as long as you have loving DSs and you're not estranged, I think you're doing ok!