How about Peter talking to his future adult self in a magical mirror?
It happens when he's exploring his father's house.
Peter doesn't often get the chance to wander around the rooms and hallways of his father's home, but his father is long asleep and Peter is curious, wanting to explore the dusty hallways and gigantic rooms.
He can feel the magic here, brimming at his feet -- surrounding him and filling him, both everyone and nowhere all at once. It isn't often that Peter is in the company of any sort of magic, so it draws him forward.
Stepping into one of the long hallways, Peter walks forward -- eyes wide, looking at everything. It seems so strange and wonderful to him, something brand new and mysterious. He's almost to the end of the hallway, when --
Peter turns, eyes widening, as he looks into the mirror in the hallway -- it's a large mirror, going from the floor to almost the ceiling, and he almost thinks that it is not a mirror, but a painting of his father -- until the image blinks back at him and smiles -- bright blue eyes glittering even in the dusk. The little boy stops in his tracks, and the image laughs.
"Are you alright? I'm sorry, I didn't mean to frighten you, little boy. It's not often, though,t aht I am able to communicate with others -- usually, it is only with my father," the image pauses, thick eyebrows lowering to his eyelids as his face softens.
"--well, our father, I should say. It's nice to meet you, Peter. My name is Peter Kirkland, and I am one hundred and eighty-four years old. It's been a long time since I've seen myself so small."