From among the Paramitas, which are the basic instructions on the path of great scope, or Mahayana, there is the Paramita of Prajna, or "wisdom." This wisdom can be subdivided into two- the wisdom of lack of phenomenal identity, and the lack of self-identity. Within that latter topic, one finds various approaches-in mainstream Gelukpa approach, one relies on a variety of analytical approaches. The other schools use these analyses, as well. That is mainstream Mahayana.
Mahamudra and Dzogchen fall in this category, relating to the wisdom of absence of identity, and in particular, to the cognizant-yet-empty Nature of Mind. Although in analysis, self or mind cannot be found, at the same time this does not resolve into a blank nothingness. Although mind cannot be found, Mind's Nature, as the cognizant awareness, able to know, cannot be denied. This is the basis of Mahamudra, and of Dzogchen, though these practices and instructions are not solely part of the Paramitayana. They are Tantric.
In Paramitayana prajna practice, one rests after the "non-finding," non-identity, while in mahamudra and Dzogchen, one rests in Mind's Nature. Some say an "idea" of emptiness should be "held," as a reminder, while those who practice Mahamudra and Dzogchen do not recommend an "idea" of emptiness.