We know this as "Night Visit" or "As I Roved Out" and play it with Em and D.

(Em)And who are you, (D)my pretty fair maid,
(Em)And who are you my (D)bonnie?
(Em)Oh, who are you, (D)my pretty fair maid,
(Em)And who are you my (D)bonnie?
(Em)She answered me right (D)modestly:
(Em)I am my mommy's (D)darlin'.
(Em)With me toor-I-ah-(D)fol-de-diddle-ah.
(Em)Die-ree-fol-(D)de-diddle-dare-(Em)I-o.

However I've heard others with a different structure for "I am my mommy's darlin".

Christy Moore does it: http://www.christymoore.net/lyrics/night.html