Bread-Bakers v101.n019.18

Alison, you may want to try looking in _Visions of Sugarplums_ by Mimi 
Sheraton, where pan dulce is given as a variation of panettone.  My edition 
of the book is the 1968 one, but I'll bet the recipe is included in the 
later version(s?) as well.  Hope this helps.    -  Ron