Honey Fungus (Armillaria melles)
It always grows in these 'clumps' and can be found on tree stumps, buried branches and dead roots of trees of all kinds. It also produces the common white rot you see on dead wood.
This fungus is a deadly parasite in woods, plantations and gardens and is certain death to any tree that becomes infected by it. It accounts for the loss of considerable amounts of commercial timber each year and is virtually impossible to eradicate once established. It can wreak havoc in gardens amongst shrubs.
It is also known as Boot-lace Fungus as it has long black cords that spread underground to infect new trees.
It is a very common species. The fruiting bodies appear in late summer and early autumn and are edible when young but become toxic with age.