It's parsley sauce...and here comes the but....the water they use to make it is the stuff left over from boiling the eels, so technically eel juice and parsley. What's not to like?
Pie and mash is nice enough if you're a heathen like me and opt for gravy instead of liquor.
What's not to like????? The bleedin eel juice that's what! Wrong wrong wrong bleeeaauuugh!