What I'm about to say is from my own experiments and others may have had different experiences. You have to make sure there's a couple of different growth areas on the sinningia tuber. See the photo showing two areas of new sprouts on one tuber. Cut between those with a sharp knife. Some people let a callous form on the cut areas by leaving it out in the open on a shelf for a while, but I don't because often the little sprouts wilt terribly, particularly on micro or mini sinningias. I plant them immediately with moist perlite on the wound area.
What surprises me is how large those micro-miniature sinningia tubers can get! Often I see there are partial formations of tubers with sprouts, but checking them later, they haven't formed anything that can be separated except with a knife. So when there is a large bump area with a sprout, I can remove that if what is removed will be at least the size of a pea, and placed it in very moist perlite in an enclosed container. I put moist perlite around the base of the sprout, too. The thing is, you need some of that old rough outer "skin" area in order for it to work. I'm not sure what that's called, but if it were a potato I'd call it the peel. The roots come out of the top layer or "skin". So when you cut the tuber, make sure you get plenty of skin layer area on at least one side of the sprout, but it's best if there is skin surrounding the sprout.
In the past I've cut up a gigantic sinningia tuber to experiment. The roots came from the skin not from the starchy callous area. The last photo I included is a miniature sinningia and had no roots coming out of the starchy calloused area when I checked it a couple of months later. The roots were coming out on the side with the original outer skin intact.
I happen to love to eat raw potatoes without putting salt on them, so I tasted a sinningia tuber. Not tasty at all. Not sweet either. I'm sure a lawyer would say I have to announce, "Don't try this at home" because you may have an allergic reaction! I taste various gesneriad nectar quite a bit out of curiosity, but wasn't allowed to announce that in my AV Magazine Gesneri-Advice column years ago because it was suggested someone might have an allergic reaction...and I agreed to omit that. Therefore, you're at your own peril eating tubers and tasting nectar!! I understand some gesneriads are considered hallucinogenic and some are used for medicinal purposes, so do think twice before smoking, eating, or tasting any of them. I happen to be allergic to a specific Nautilocalyx and broke out in blisters on my fingers. A friend in Sweden alerted me since she gave me seeds from her plant. She asked if I had any reaction to touching the plant and I said I got blisters. She did, too. I gave a friend Primulina tabacum and he got blisters."
BLOG NOTE: Don't eat your gesneriads. They are like mushrooms, really bad if you're not an expert.