Put a big pot of salt water on the fire, to use to get the bitterness
out of the fiddleheads.
Rinse and drain the scallops. If you have any really huge scallops,
cut them in half so they’ll cook evenly with the rest.
Since about 2008, I've been able to
buy “dry” scallops at Mike’s Fish Market at
the St. Lawrence Market; these have a lot less water in them than
“wet” ones, and are a lot easier to cook.
Wetness is their natural state, as they’re
underwater filter feeders;
but the problem with the wet ones is that if you don’t reduce their
water content enough, the outgassing steam keeps the cooking temperature
near 100°C, which is far too low.
In either case, leave them in a colander while you work on the fiddleheads.
Rinse and trim the fiddleheads. Good fiddleheads should be tightly
coiled, not show too much leaf, not have any brown or black bits,
and since you're going to snap off whatever you can of the straight
stalk, there's no point in buying ones with really long stalks.
When the salt water comes to a boil, put the fiddleheads in and cook
them until they're not quite al dente (5–6 minutes). Then throw out the water
(which will be brown), and leave the fiddleheads covered in a colander,
so that they'll be warm and dry when you need them.
Mix together the garlic powder, salt and flour or corn starch on a dinner plate.
Take each scallop, squeeze it in paper towel (if they were wet,
squeeze them firmly) to remove remaining
moisture, and roll it lightly on the plate.
You'll probably want to do this in three batches, so just do
the first batch for now.
Heat a frying pan medium-high, and add 2 T or so of butter.
When it melts, add the first batch of scallops.
There should be enough butter that the scallops look like they're
sitting in 1-2 mm (1/16 - 1/8 in) of it.
Now comes the trickiest part.
If all goes well, in a few minutes, each scallop will brown slightly
around the edges, and the butter near the scallop will brown too.
Flip the scallop over and you should see its bottom lightly browned.
If it's dark brown, or if the bottom is crisp, it’s overcooked;
cook the other side less, and don’t cook the next batch so long.
Let it cook for another minute or two until the other side is browned
(it won’t take as long to do the second time) and then remove from heat to
a large, warm bowl.
If you're not sure if it's done, you can try cutting one open, but
just one.
It should look like it is just on the verge of losing its translucence
on the inside, and it'll lose it completely in a few minutes even when
removed from the heat.
You can also use the jiggle test: if you tap it with a fork in the pan
and it jiggles, then it's done.
If it's raw, the shock wave from the tap gets absorbed by the uncooked
middle.
That was if things go well.
What can go wrong?
If you're getting dark brown or black bits in your butter, the heat is
way too high. Fish them out if you can, and turn the heat down.
If you're getting a foamy mess in the pan, you didn't drain the
scallops well enough, or had the heat too low.
If you have enough uncooked scallops left, you can clean the pan and
start over, but otherwise you're stuck, so don't let this happen.
If the scallops are rubbery, you cooked them too long.
If they're squishy, you didn't cook them long enough.
Do the remaining scallops in batches, adding butter as needed as the old
butter boils off. At the end, put the fiddleheads into the butter, and
finish cooking them, adding about half the lemon juice to taste.
Add the fiddleheads to the scallop bowl, add fresh black pepper
and more lemon juice to taste.
You can try folding (mixing) the dish a little, but be careful:
the more you mix it, the more you’ll lose the garlic coating
off the scallops, costing you both flavour and appearance.
Eat immediately.