There is really no flavors there, except salt, mustard and butter. Only thing that brings it´s own flavor to the table is carrot.
My family loved it, so we had it maybe once a month when I was a kid. Think it´s the only traditional danish dish that I dislike.
I think the dish goes back to when you had to salt the meat to preserve it, and eat it with home grown veggies.
The picture is from a cookbook, so it´s supposed to promote it.