The Food Lab: Better Home Cooking Through Science

gratin, I pack them into a greased casserole dish standing on
their edges, working my way around the perimeter of the
dish and packing it all in tightly. Because potatoes vary
wildly in shape, you end up with tons of little nubby bits
sticking out all over the top surface.
As the potatoes cook, the cream eventually starts to boil,
simmering up and over the tops of the potatoes, basting
them as they roast, aiding further in preventing them from
getting leathery. A final layer of cheese added halfway
through the uncovered stage of cooking adds a layer of
flavor to the final casserole.
During the final stages of cooking, the cream eventually
loses enough moisture that it breaks, releasing its butterfat,
which coats and then gets slowly absorbed into the potatoes
as they continue to lose water content. Milk proteins in the
cream and the cheese coagulate, creating little pockets of
curd-like tenderness between slices. The final dish is
nothing short of glorious. Look at it. I mean, look at it.
Every bite has a combination of crisp-but-moist upper
potato ridges and rich and creamy potatoes underneath with
a cheese underscoring the whole affair.†
It’s so good that I’ve decided to make this only in the
middle of the night while my wife is fast asleep and finish it
all myself, picking at the crispy cheesy bits around the
edges of the casserole dish in the wee hours of the morning,
leaving just enough to hint at the glory that it once
contained. What dear? What’s the lingering aroma of garlic
and thyme in the air, you ask? Ah, well, you snooze you
lose, hon.