but wait for the gift my Father promised, which you have heard me speak about. 

名词the gift被限制性定语从句（that）my father promised修饰，which引导的非限制性定语从句修饰的是the gift my Father promised，即我父亲答应给我一个礼物这件事。which在定语从句中介词about的宾语。从句为感官动词后接复合宾语，为hear sb do sth结构。me 为宾语，speak about (which)为不带to的不定式作宾补。