Correct, the Revitalization therapy.
QUOTE
Revitalization (Augmentation p.88-89)
Revitalization is a recent breakthrough that repairs Essence loss derived from invasive implantation. Universal Omnitech is trying to keep the mechanism a secret, though geneticists have speculated that the effect is achieved by performing some kind of “genetic feng shui.” The theory is that scientists realign qi from
astral shadows by genetically remodeling DNA to repair damage to the aura or balance to the body’s systems, and thus the patient
regains Essence.
In game terms, revitalization regenerates the Essence “hole” left by the removal of an implant from the body. Revitalization is slow and Essence is restored by recurring gene therapy sessions ata rate of 0.1 Essence per month. Though Essence points lost to implantation, Energy Drain, and addiction may be restored through gene therapy, Magic/Resonance points lost are never returned and reductions to the maximum Magic/Resonance attribute remain in effect.
Revitalization can be performed without permanent hospitalization during the treatment time. Characters have to spend at least 7 days per month in the clinic to continue the treatment. If the character has not attended the clinic for two months the treatment stops and has to be started anew (including the starting costs) to continue the effect. Note that this treatment cannot be attempted if the implant is still present.
...all of it at the low, low price of 75,000 nuyen with an additional 20,000 nuyen per month!
So yeah; make it your runner's long term goal, or their major investment when they retire.