I'm curious about this Uncommon White Tara Empowerment. She seems to give it quite often.
Does anyone here know anything about it?
It's an Annutarayoga tantra White Tara that may come from Jamyang Khyentse Wango. This
is the RigaWiki entry. Generally Sakayapas don't talk about the details of higher practices and Khenpo Kalsang said next to nothing about it. So it's a kind of secret practice to some extent although HE Jetsun Kusho-la gives it often.
It is not really that secret at all.
The origin of the practice is Bari Lotsawa, passed through the Kagyu lineage (Gampopa apparently extended his life with this practice) until it rejoined Sakya during the period of Tsarchen Losal Gyatso. It was one of Khyentse Wangpo's very important practices and he supposedly possessed a thangka of White Tara that could speak.
It is a very wonderful practice, but it is quite complicated in terms of the visualization. Khyentse Wangpo composed a teaching manual on it, that is spread out over one week or so.
The essential visualization of the protection cakra is combined into Dzogchen Community Tara practice. So receiving this initiation and practice is a good support for the DC practice.