You're lucky to have witnessed it. :)
I'm yet to see one. Here in California, we've only come across the red and the pink Epiphyllum cactus varieties. I too have the pink one, but it is a small plant. God knows when that might bloom. :)
Brahma kamalam is a very unique flower that blooms at night with a pleasant fragrance. It is said to be very special for Lord Shiva. I was very happy to see them bloom. Just one leaf is enough to start a new plant. I am sharing the different stages of the flower. This is a bud