What is Maillard browning?

oven spring

The dramatic rise in the first 10 minutes of baking, as trapped fermentation gas expands, water flashes to steam, and yeast does its last burst before dying around 140°F / 60°C. Most of a loaf's final volume comes from oven spring, not from bulk fermentation. The crust has to stay pliable long enough for the rising interior to push outward — which is why steam in the oven matters so much for hearth breads. A dry oven sets the crust early; the interior expansion has nowhere to go and the loaf comes up short. Scoring also affects oven spring: a well-placed cut gives the expanding gas a designed exit so it lifts the loaf at the score rather than blowing out a weak seam.

brown butter

Butter cooked past the melting point until the water content evaporates and the milk solids toast on the bottom of the pan, turning golden brown and developing nutty, caramel-edged flavors. Called beurre noisette (hazelnut butter) in French. Cooked at medium heat with frequent swirling, usually 8-12 minutes total: the butter melts, foams, quiets, then the milk solids hit the bottom and start browning — pull from heat the moment you smell nuttiness. Browning evaporates ~15-20% of the butter weight as water, so browned butter weighs less than the raw amount you started with. Used in brownies, financiers, and chewy chocolate-chip cookies for depth that plain melted butter cannot produce. ⚠️ Pour hot brown butter into metal or ceramic — glass containers can shatter, especially in an ice bath cool-down.