Thanks for the question.

When I enlarged your picture, I could not see any obvious presence of mushrooms. In this same context, I do not understand your statement that the Christmas cactus “…..is growing mushrooms”.

I think that your plant could benefit from being moved into a larger pot. A Christmas cactus generally prefers to be slightly root-bound, so choose a pot that is only one size larger than the one in which you are currently using. For example, if your cactus is in a 4-inch pot, move it up to a 5- or 6-inch pot. Make sure the pot has good drainage, as Christmas cacti don't like to sit in waterlogged soil.

Alternatively, you could try dividing the plant into two smaller clumps and moving each clump into their own pots. The best time to divide a Christmas cactus is in late spring or early summer, after it has finished blooming and before the growing season starts. This timing allows the plant to recover and establish itself before the next blooming cycle. So this is not an approach that may be feasible at this time (early August 2024).

See the following for further information on these and related points:

https://www.goodhousekeeping.com/home/gardening/a20705680/christmas-cactus-care/?utm_source=google&utm_medium=cpc&utm_campaign=mgu_ga_ghk_d_bm_prog_org_us_a20705680&gad_source=1&gclid=CjwKCAjw2dG1BhB4EiwA998cqCNtuK7-p2QjJC8HiI_VacekO6B7cwE0stbFMi94lpXXT-Daru81RxoCOIMQAvD_BwE

https://www.almanac.com/plant/christmas-cactus

https://www.thespruce.com/how-to-repot-a-christmas-cactus-7570598

Good luck. Please get back to us if you wish regarding clarification of how your plant is growing mushrooms.