Hello my friend
The first thing to do is to cut all the parts affected by the mushroom, with several centimeters of safety margin.
It will then be necessary to use a maximum of ventilation to limit the humidity, and to harvest quickly by monitoring very regularly that the mold does not return.
The parts of the plant affected by the fungus should not be consumed, because there is a risk of pulmonary infection.
After the harvest it will be necessary to clean all the space of culture as well as the material (pots ...) with bleach, to eliminate all the traces of the Botrytis.
There are certain fungicidal products that are very effective against Botrytis, the best being probably Botryprot.
It is also possible to use beneficial microbial life that will fight directly against Botrytis, such as Trichoderma Harzianum, Ulocladium Atrum or Gliocladium Roseum, as a direct spray on the plant.
May the force be with you 💪