Cat Napper (5e Feat)
From D&D Wiki
Over the course of your travels you find it easier to relax or fall asleep in new places much faster. When taking a short rest, if you expend hit die to heal, you recover double the hit points you would recover otherwise. If the amount rolled on a hit die would heal you for more than your hit point maximum, you gain temporary hit points for one hour equal to the amount of hit points you would gain over your hit point maximum.