Boston brown bread — a dark, dense, moist bread made from rye flour, cornmeal, whole wheat flour, molasses, and buttermilk, steamed (not baked) in a covered mould or a tin can for 2-3 hours — is the traditional accompaniment to Boston baked beans and one of the most unusual breads in American cooking. The steaming technique produces a bread with no crust — uniformly moist, dense, and dark throughout, with a flavour dominated by the molasses and the earthiness of the rye and cornmeal. The bread's origins are Puritan: steaming required less fuel than baking (important in a New England winter), and the grain combination (rye, corn, wheat) used the three grains most available in colonial New England. The practice of steaming in a tin can — a 1-pound coffee can, greased and filled two-thirds full — became the standard home method and persists today.
A cylindrical, dark brown bread — the shape of the can or mould it was steamed in — with a uniform, moist, cakelike crumb, no crust, and a deep molasses-rye-corn flavour. When sliced into rounds and served alongside baked beans, the bread is slightly sweet, earthy, and dense enough to absorb the bean sauce without falling apart.
Baked beans (AM2-04). Always. The brown bread absorbs the bean sauce and the combination of the molasses-rye-corn bread with the molasses-pork-beans is a flavour loop: the same sweetness and earthiness reinforced from two directions.
1) Three grains: rye flour, cornmeal, and whole wheat flour in equal parts. The combination produces a complex, earthy flavour and a dense texture that no single grain achieves. 2) Steaming, not baking — the mould (tin can, pudding mould, or any tall, narrow, oven-safe container) is greased, filled two-thirds, covered tightly with foil, and placed on a rack in a pot with 2-3 inches of simmering water. The pot is covered and the bread steams for 2-3 hours. The result is uniformly moist with no crust formation. 3) Molasses and buttermilk — the molasses darkens the bread and provides the signature sweetness; the buttermilk's acid reacts with baking soda for leavening and adds tang. 4) Raisins are traditional — folded into the batter before steaming.
B&M canned brown bread — available in grocery stores throughout New England — is a steamed-in-the-can product that is genuinely good and serves as the baseline standard. Homemade is marginally better; the convenience of the canned version is significant. Brown bread sliced into rounds, spread with cream cheese — the New England afternoon snack. The bread can be steamed, cooled, unmoulded, and then sliced and lightly toasted on a griddle. The toasting creates a slight crust on the exterior while the interior remains moist. This is the version that converts skeptics.
Baking instead of steaming — the result is a different bread entirely. The steaming is the technique. Removing the cover during steaming — the steam must be trapped to cook the bread evenly. Peeking extends the cooking time. Not greasing the mould — the dense batter sticks tenaciously to ungreased surfaces.
Fannie Farmer — Boston Cooking-School Cook Book; James Beard — American Cookery