This tool is called by two separate names: self-parenting or re-parenting. I prefer self-parenting as these techniques were not known by my birth parents.
Reparenting to Heal the Wounded Inner Child
How To Reparent Your Inner Child And Become More Secure
7 Books That Will Help You Heal Your Inner Child
Today, I honor myself as a mother to myself.
Emotional Sobriety Means Healing Mind, Body, and Soul 