I suspect that the seven minutes quoted in the previous comment will
produce a very soft egg, which may not be to your taste if you like
the white "solid".
Goose eggs can be four or more times the size of a hen's egg. Since
the guru of the British kitchen, Delia, recommends boiling a chicken
egg for four minutes to give "a white that is just set and a yolk that
is creamy", I rather doubt that seven will achieve a well-set white in
a goose egg.
Note this person's comment (about hard boiling eggs):
"My experience is that you can boil goose eggs all day and they still
have a soft yolk center! Really, by the time you boil them long enough
to get them solid thru the yolk, the whites are like rubber tires."
I thought I would be able to answer this as I have watched my husband
cook and eat a goose egg, but neither of us can remember the exact
timing. However, I do know you cannot start with cold water for a
soft-boiled egg and, yes, it does depend on the size of the egg.
Even Mrs.Beeton, the Victorian "household management" authority, was
no help, though she discusses duck and plover eggs.
While searching for information I've come across a lot of discussion
on the subject of goose hygiene. Some people are nervous of using
goose eggs unless they are very thoroughly cooked. Others think you
shouldn't worry unless the geese have been laying their eggs in mud
with goose dirt in.
Maybe another researcher will be able to come up with something more
exact. Otherwise, you may have to resort to a bit of trial and error.
Hope you enjoy the results!
Passing on some notes I made on relative egg sizes:
Goose eggs look a bit alarming because of their size, and it takes a
while to get your head round the idea of eating one. They weigh
between three and a half to four times the weight of a large hens egg.
Not terribly suited for your brekkie egg, but fine for a frittata or a
1 duck egg = approx. 2-3 chicken eggs
1 goose egg= approx. 2 duck eggs or 4-6 chicken eggs
..if you have access to, and want to cook other types of eggs (goose,
turkey, duck), then allow extra time for size. If you are baking, the
best way to measure is by comparing the eggs you are using, weight for
weight, with hens' eggs to give you a guideline.