Why are most rich doughs mixed using the sponge method?

The sponge method is often used for rich doughs primarily to promote fermentation before the addition of fats and sugars. This technique involves creating a sponge or pre-ferment, which is a mix of flour, water, and yeast that is allowed to ferment for a period of time before incorporating the remaining ingredients. During this fermentation phase, yeast begins to act on the sugars present in the flour, producing carbon dioxide and alcohol, which contribute to the dough's flavor and structure.

By allowing this initial fermentation to occur, the dough develops a more complex flavor profile, as well as improved stability and extensibility. When fats and sugars are added later in the mixing process, they can hinder the yeast's activity if added too early. Thus, mixing rich doughs using the sponge method allows for optimal fermentation and flavor development before the rich ingredients are introduced.

In contrast, focusing solely on simplifying the mixing process does not address the need for proper yeast fermentation, and while enhancing flavor is a benefit, it doesn't capture the primary purpose of the sponge method. Achieving a lighter texture is a goal of the dough, but it's the fermentation process that significantly contributes to achieving that quality.