Pain de mie is what English speakers would consider regular sandwich bread. It is sold in French supermarkets sliced and packaged.
It has sugar in it, making it sweeter than other French breads, but not as sweet as normal North American commercial breads, which have a lot of sugar in them by anyone’s standards.
It is made from wheat flour, water, salt, fat, sugar, yeast, fava bean flour, ascorbic acid, and emulsifiers. It is white inside, and the fat gives it a finer, tighter crumb than other French breads.
It is usually made industrially, though it can be made at home by hand or with bread machines, just as we would. It is sold in rounded shapes or square, rectangular loaves. The French use it for toasting, for making fancy sandwiches with, and its shape and thickness makes it ideal for Croque-monsieurs.
The square, rectangular loaves are cooked in lidded breadpans. The lids both ensure uniform slice sizes and, by constraining expansion of the dough, further help to ensure a tighter crumb. When cooked in this fashion, Pain de Mie is almost identical to what Americans call “Pullman Bread”, depending of course upon the recipe used for the Pullman Bread.
Pain de mie 100%
This is a pain de mie with no crust on it — presumably either baked in a sealed pan so that a crust can’t form, or with the crust cut off afterward at the factory before packaging.
Some English-speakers occasionally think that the 100% might refer to the healthy nature of the bread, mistakenly thinking that it means something like “100% whole wheat.” Instead, what the 100% means is “100 % mie” — that is, 100% “crumb” or inside, meaning therefore “no crust, no outside.” Just pure white crustless bread, perfect for mothers who are tired of having to cut crusts off sandwiches for their younger children.
Pain de Mie keeps fresher longer than other French breads owing to the fat in it, which other French breads usually lack. Freezes well.
The French “blame” English speaking tourists for introducing Pain de Mie at the beginning of the 1900s. Nevertheless, they buy it in great quantities, and like how it keeps better than other breads.
“Mie” means crumb in French — crumb as in when someone refers to a bread as having a “coarse crumb” or a “fine crumb”.
Presumably it’s named this to call attention to the particular fineness of the crumb, as compared to the coarser crumb in other French breads such as baguettes or pain de campagne, for instance.