"Muggen sopp i skogen" are moldy mushrooms in the wild.
The Henrik hates the "muggen sopp i skogen", and whenever he sees one while he's on the tur in the skogen, he goes into a temper tantrum and gets a heart attack afterwards, nobody knows why.
Person: Hey Henrik, i think i see a muggen sopp over there, in the skogen.
Henrik: LASJHKØGYAJHKSLØDFYUGASBHJKFGHAVJSDKPDH NEIIIIIII JEG SKAL BANKE DEG ASKODJIUHASJID, FUCK MUGGEN SOPP I SKOGEN!!
Used to describe a pair of breasts that are both large like a cow and sopping. Sopping being an onomatopoeic word that cannot be precisely defined as it depends on context. Especially recommended for describing the rack of a girl having well formed and large boobs, typically by way of breast implants or just naturally massive melons, but also the jugs themselves must be sopping in some way. Very useful in situations in which describing the breasts literally would be onerous or cumbersome.