For several years, whenever Santa came to our home on Christmas Eve, he could count on a plate of homemade holiday cookies, a few carrots for his reindeer and a letter from my daughters.

The girls were younger then, elementary school children at the height of their innocence. They believed in Christmas without reservation, every part of it. The world had yet to reveal itself as a place where wonder is a rare thing.

Santa often wrote back to them. On Christmas mornings, before the girls opened presents, they would quickly read the thank-you note he left by the cookie crumbs on the dining room table.

"I want you to know that I’ve watched the two of you all year and I am always impressed with how much you love each other and how you look out for each other," Santa told them in his 2001 note. "Don’t ever stop being each other’s best friends."

The girls never kept the letters. It was enough that Santa wrote them.

They’re grown now, young women with adult concerns about relationships, college and careers. And they’re not as sentimental as their father.

I kept the letters because they spoke to me of childhood — theirs and mine. I kept them because innocence is worth remembering, especially at Christmas.

The letters were stashed so deeply in my personal archives that they were practically lost — tucked in an envelope that was inside a box on a high shelf in a closet. Finding them, as I did recently by accident, was like finding a time capsule.

Their comments transported me to simpler times.

"Dear Santa, How are you? I’ve been a good girl this year. I listened to mom and dad all the time — well, maybe not all the time. But I’m trying now."

"Santa, could you please get something for my little sister?"

"Sorry we don’t have any snow-top cookies (the ones we got from Mrs. Claus) because somebody ate them all."

"I wonder what an elf’s life is like?"

"Merry Christmas!"

"P.S.: Don’t forget my picture of the North Pole!"

Because they were handwritten — first in careful print and then in flourishing script — the letters bear unmistakable marks of childhood. The girls wrote letters with happy faces, ended sentences with large exclamation points and included drawings of each other.

At one point during the annual Christmas exchanges, email addresses were shared, too. Believe it or not, Santa had a Hotmail account. This came in handy for my younger daughter, whose emotional growing pains included arguments with her big sister.

Santa became a reliable pen pal.

He told her to be patient. She said she would. He told her that her sister loved her. She said she knew that but Santa, sometimes she makes me so mad. And so sad.

Santa said he understood, he really did.

This went on for several months. By Christmas that year, my younger daughter wanted to thank Santa. She asked her mother to buy him a nice T-shirt. Something with a Hawaii theme. She wrapped it with a bow and placed it beside the cookies on Christmas Eve.

She included a note, too.

"Dear Santa, here is a present for you," she wrote in her best script. "Since you always give stuff to me, I thought it was your turn."

Santa was ecstatic. Over the moon.

And then he realized he had a problem. For the first time Santa had no idea how to say thank you. He wanted to say it with a gift, but what should he give? No ordinary gift would do.

In his panic, Santa was hardly original.

He knew my daughters were fond of the children’s book "The Polar Express," by Chris Van Allsburg. It’s a story told to millions of children every Christmas Eve and my daughters always expected to hear it before bedtime.

For the girls, "The Polar Express" was a tradition, just like the cookies and the letters. They never tired of hearing about the boy who is whisked to the North Pole on Santa’s magic train and how the boy discovers the meaning of Christmas in a sleigh bell cut from a reindeer harness.

So Santa left a bell with the plate of cookie crumbs. The bell was painted red and chipped from use, but it still tinkled when you shook it. He left a note as well.

"Love is the most powerful magic of all," he wrote. "But you already know that."

The T-shirt was a gift he would treasure even if he never got to wear it in Hawaii.

"Mrs. Claus may be cross at me for having to replace the bell, but I wanted you to have it," he wrote. "I hope it will remind you of the magic of Christmas."

Of course, he signed the letter: "Love, Santa."

The next year was the last time Santa found a Christmas Eve note on the dinning room table. My younger daughter wrote it. She thanked him for the presents she hoped would be there when she woke up.

"I hope you email me soon," she wrote. "I like it so much when you write to me."

The letter included an apology: There was no gift for Santa because she had run out of time.

What she never knew was that a letter was the only gift that really mattered to Santa.