Q.My potatoes are growing underground but there are no shoots or leaves?????
Ok, so I planted my potatoes about 7 weeks ago and nothing appeared to happen. I thought they had just not grown. I carefully dug down to them expecting to find a rotten potato. To my surprise I found a load of new little potatoes which seem to be thriving. I have never seen this before and have no idea what is happening here. Can anybody give me a heads up please.

It sounds like the soil or planting medium was not able to support growth. The underground growth you mention was likely the potatoes trying to grow, using the material stored in the tuber, but that's as much as they managed to do. The leaves never developed properly, nor did the roots.
This link will refresh you on growing potatoes.