Endurance Caster (5e Feat)
From D&D Wiki
Prerequisites: Constitution 13 or higher, the ability to cast at least one spell
You are a spellcaster capable of exchanging your vitality for magical power. During a short rest, you can spend hit dice to recover spell slots. The amount of hit dice required equals the level of the spell slot.
The maximum level of spell slot that can be recovered using this feature equals your Constitution modifier (maximum of 3rd level).