When we look at the essence of our mind we are talking about not following after any thoughts of the past, nor looking forward to any occurrences in the future, but focusing on the very present moment of awareness.  For instance, right now, I am talking to you and you are listening to me.  That awareness of listening is present in your mind this very moment.  We are talking about focusing on essence.  What is the essence of our present mind?

The essence of our mind is clear and aware and can never contain concepts.

Written by Khenpo Karten Rinpoche in the book Precious Teachings, the chapter entitled “Sunyata, Essence of Mind” page 96 in the paper copy, and page 103 of the PDF version.