Fungi at base of an Oak

Fungi at base of an Oak

Observation - Fungi at base of an Oak - UK and Ireland. Description: This fungi was at the base of an Oak tree in a garden. Above it was a white fungi that looked like a ping pong ball. Any ideas what it is?

This fungi was at the base of an Oak tree in a garden. Above it was a white fungi that looked like a ping pong ball. Any ideas what it is?