Ah. I think I saw this done on This Morning about 10 years ago.

You cut it in half by rotating the knife through it (around the stone) and then twist it to seperate the two halfs from the stone in the middle. Then you cut a criss-cross into the flesh of your half-mango. Next you turn the half-mango inside out. It should now look like a fruity hedgehog. Just chop the spikes off.

Am I thinking of a mango? I think so. Hope that works out for you.