I prefer traditional 'yum cha' breakfast - there are lots of places that open very early for leisurely breakfast. Two of the more 'popular' known places are:
Maxim’s City Hall is located at City Hall, 2nd fl. (Edinburgh Pl.), Hong Kong, Tel. +852 2521-130, www.maxims.hk
Victoria Seafood is located at 2nd floor, Sun Hung Kai Centre, 30 Harbour Road, Wan Chai, Tel. +852 2827 9938 Hopefully others can recommend their favorite place.