Reading people's minds tends to bring with it all manner of extraneous information, Charles Xavier has found, as well as whatever it was he might have been looking for in the first place. All the little snippets that make up a person's consciousness, along with their memories and their thoughts, little things like Moira's favourite book and where Hank goes to get his shoes made, names and addresses of favourite aunts and childhood friends, social security numbers and dates of birth. Charles doesn't always retain this sort of information, irrelevant as it usually is to his purpose, but some things seem to stick.
Even things that their owners think they've forgotten, sometimes. Like the fact that two weeks after they'd all moved into the mansion, Charles realised that Erik's birthday was approaching, and yet he hadn't said a word or even given it a thought. Carefully, quietly, Charles glanced into Erik's mind, although he had already come to the conclusion that his friend probably hadn't celebrated his birthday in years, possibly not since the time of those few faint, bright memories to which he had been trying to grant Erik access, slipping around the blocks and bolted doors his friend had installed inside his memory. Sure enough, there was nothing there when he looked, not even the consciousness of the day's approach, and Charles had to wonder if his friend had forgotten it entirely.
Well, not quite entirely. It must still be part of his awareness, otherwise Charles wouldn't have picked it up. But it was clearly not something he was even in the habit of thinking about any more.
Charles couldn't quite understand that; not a single one of his birthdays had gone unmarked, extravagant presents from his mother and stepfather to paper over the cracks between them, and in later years cards and silly little gifts from Raven, sometimes useful and sometimes not but always well chosen, always displaying the thought she'd put into the choosing, and how very well she knew him. He couldn't imagine not having a birthday. Nor could he quite bear the thought of his friend being so alone in the world for so long that he had fallen so completely out of the habit of celebrating his birthday, nobody there to send him a card or buy him a gift, nobody to think of him at all.
He had enough common sense and self-preservation to know that Erik wouldn't want a fuss. Nor would he want the others to know. It would have to be something subtle, something careful, something that was just between the two of them; and if Charles was honest with himself, he liked that idea very much indeed.
The choice of gift took a long time, and he spent many hours turning over possibilities in his mind, considering and rejecting every single one; what did one buy for a man like Erik, anyway? He already seemed to have everything he felt he needed, so perfectly happy with his minimal possessions that Charles felt a little self-conscious at the ostentatiousness of the mansion, packed to the rafters with generations of his family's collections, books and paintings and sculptures and tapestries everywhere you looked. And how to hand the gift over, once it was chosen? No fuss, no ceremony, that was for certain, and Charles wasn't sure that he could quite handle it if Erik rejected his gift, or not to his face, at least.
After long and careful consideration, though, an idea came to him, and a purchase was made, left on Erik's bedside table while he was out, a bottle of the best whisky Charles' wine and spirits dealer could supply, with a card that simply read "A toast to friendship, and to many happy returns of the day".
Erik didn't mention it, but then he didn't have to, and he probably knew it. Charles felt the very moment he discovered the bottle, felt the confusion give way to surprise and, deep down, a flash of warmth and appreciation. That was enough. No fuss.
The bottle was left behind, of course, after their abrupt parting. It wasn't exactly the sort of thing to take on a mission, after all, and Erik did not return to pack his things afterwards. So it stayed in his room, and Charles thought that Erik had forgotten about it, resigning himself to the idea that perhaps it hadn't meant so much to Erik after all.
Until, that was, his own birthday, four months or so after the crisis, when a package arrived addressed to him in careful, anonymous capitals. He'd had a card from Raven, the postmark blurred and indistinct, no message beyond the printed 'happy birthday' and a neat little letter R; but he hadn't expected anything else.
Charles made sure he was alone when he opened the package, made sure his psychic defences were locked right down. He didn't want to broadcast anything, accidentally, if his suspicions were correct.
The brown paper enclosed a box, sturdy and wooden, and inside the box, beneath the straw packing material, Charles discovered a bottle of the very best whisky, identical to the one which still stood upstairs in Erik's old room. There was no card, but he told himself it didn't matter. The gesture was enough.
The following year, he had been able to glean enough information to be able to send Erik's bottle of whisky back to him, with a light-hearted note to the effect that Erik appeared to have forgotten to take it with him, and that Charles assumed that he would like it back. Charles hoped that he wasn't overstepping the mark, but on his own birthday another bottle arrived, with a similarly light-hearted note thanking him for his trouble and hoping that the enclosed would make up for it.
It became a habit, or a tradition, over the years that followed. No matter what happened, how desperately opposed they had been over the intervening months, Charles always sent Erik a bottle of the very best whisky for his birthday, and always received one in return on his own birthday. Sometimes they were on good enough terms to share a glass or two over a game of chess; sometimes they were not. It didn't matter; they both knew that the bond between them was unbreakable, despite everything. The gift of whisky, twice a year, only confirmed it, serving as a reminder when they needed it that their friendship ran deeper than their enmity.