I'm planning on making a display cake, 4 tiers (bottom tier 10in round, 10" diameter sphere, 8in and then a 6in top tier). The "sphere" in the middle has to be made either out of cake, RKT, or another edible material. I would like to know the best way to carve the RKT into a sphere shape...should I sculpt the two halfs and then glue them together, or make one giant piece and carve it into a sphere?

Also, what would be the best way to support the two tiers that will sit on top of the sphere? Fortunately, the cake dummies aren't as heavy as real cake, but I am still concerned and don't want any weight on the RKT sphere....any help would be greatly appreciated!

Hi
From experience I have managed quite nicely to actually manipulate and 'roll' the rkt into a ball shape, carving for smoothness where needed. I would suggest after the ball shape is achieved, coat with a layer of butter cream and place in fridge for a short time to set. Cover in your fondant then push 3 dowels through in the shape of a triangle long enough to go through the tier below and just so it will hold the cake above much like you would for a regular tiered cake, they need to be placed close together so they do not 'show' under the cake on top.
Hope this helps and good luck.

I agree with Karen, Id say soften your RKT in the micro for 10-20 seconds then with wet hands roll it into a ball, then Id wrap it in cling wrap and keep twisting the wrap tighter and tighter so you really squeeze that RKT into a tight ball. Peel off your cling wrap before chilling else it sticks! You may need to put your dowels through at this point as sometimes after chilling, hammering dowels through can shatter your shape.
I tend to find coating RKT with white chocolate works better than BC- easier to handle when dry and lots stronger.
HTH