Your plant is a variety of Hoya pubicalyx, figuring out the cultivar name isn't really important as they all require the same care. If I had to guess I would say Hoya pubicalyx 'Royal Hawaiian Purple'.
Hoya pubicalyx is a close relative of Hoya carnosa, pubicalyx coming from the Philippines where as Hoya carnosa is from China.
Hoya pubicalyx 'Black Dragon' is a new introduction that was collected in the wild and not simply a horticultural variety. It has only been available for a few years so it's not a common plant at all. The leaves of this one are always solid green unlike many of the other Hoya pubicalyx varieties.

Mike

I think it's a nice photo, Amelia. You certainly have some gorgeous blooms there. I would be super happy to get such charcoal-y flowers out of my publicalyx. :)

Your description of the leaves as starting out dark also fits with Mike's RHP postulation. This plant is known for lots of chocolate and wine colored leaves.

As Mike says, Black Dragon's leaves are pretty but a very boring flat green. It might not even turn out to be a publicalyx. Also, it doesn't always bloom black either, as some of us have been disappointed to discover. Bloom color can fluctuate wildly depending on the plant's conditions.

If you really do have a RHP, it's a very interesting plant in this respect and often shows vivid watercolor splashes of various colors on single flowers, or very different colored blooms right next to each other.

Happy growing and thanks for sharing your Hoya story with us!