I have been researching this on Google, and I think there is a process. What is this process called? I have forgotten.
You are probably thinking of a pair-instability supernova. Such a supernova releases more energy than the star's gravitational binding energy, completely disrupting the star and dispersing the contents. Meaning that with nothing else in the universe, over infinite time every particle from the star will get infinitely far away from any/every other particle. The mass, energy, etc. of the star doesn't vanish from the universe, though; it just gets spread throughout it. But there will be no dense remnant left behind: no dwarf, no neutron star, no black hole; over long time scales there won't even be a discernible nebula remaining (though note the star may have shed off significant amounts of material prior to this event, which would interact with the ejecta and may result in some sort of permanent structure suggesting a star used to be there).
A Type Ia supernova (SNIa) also normally leaves "nothing behind" (that is no dense remnant; all the material of the stars involved gets dispersed into space.) This phenomenon involves one or two white dwarf stars, in which a significant fraction of the material (initially usually carbon and oxygen; although a substantial fraction of He, Ne, Mg can also be present) undergoes fast thermonuclear burning (perhaps detonation involved too) into 56Ni, 28Si, calcium and other elements lighter than Ni, all this burning taking ~2 seconds. The thermonuclear energy released unbinds the white dwarf(s), the reaction products expand into the Universe; thus SNIas enrich the interstellar medium (ISM) with the heavy elements produced, drive shock waves in ISM, and entertain astronomers.