Published November 1, 2005.
Replacing the butter and cream with buttermilk doesn't work. (Unless you like curdled, parched spuds.) So what's the secret to tangy, creamy mashed potatoes?
Merely replacing the butter and cream with buttermilk to create tangy, creamy buttermilk mashed potatoes doesn't work--the finished potatoes are curdled, crumbly, chalky, and dry.
We wanted mashed potatoes with buttermilk's trademark distinctive tang, but we also wanted mashed potatoes creamy and flavorful enough to be worth eating.
Many recipes for buttermilk mashed potatoes remove so much butter that the potatoes taste lean and lack creaminess. We started by restoring just enough butter to save our mashed potatoes from this fate. We then tackled the curdling problem. Buttermilk curdles at 160 degrees; a temperature reached almost instantly when the cold liquid hits steaming-hot potatoes. By adding the butter, melted, to room-temperature buttermilk, we coated the proteins in the buttermilk and protected them from the heat shock that causes curdling. We also simplified the recipe by choosing peeled and cut Yukon Gold potatoes rather than using unpeeled russets (our usual choice for mashed potatoes). Because Yukon Golds have less starch and are less absorbent than russets, they don't become soggy and thinned out when simmered without their jackets.
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