Frozen/Preserved mobs

Frozen/preserved mobs that could be brought back to life. These mobs/structures would be buried in upper layers of snowy biomes (so they don't interact much with cave biomes), and would consist of a box of mineable but unobtainable blocks with the mob + ice. Once you dig a space under it, you could then use a weak source of heat to melt the ice but not burn the mob, after all the ice has melted, the mob would be in a somewhat frozen state and then you could use a potion to bring him back to life (and now it would behave like a normal mob). If you break any of the blocks of the structure that contains the mob, the mob would become unobtainable.