Siberian or pink purslane, Claytonia sibirica
The leaves can be eaten raw or cooked. They usually have a fairly bland flavour and are quite nice in a salad or cooked as a green vegetable.
The leaves have a distinct earthy after-taste rather like raw beetroot. They are available all year round but can turn rather bitter in the summer, especially if the plant is growing in a hot dry position.
Although on the small side, the leaves are produced in abundance and are very easily harvested.