Friendship Prune Cake

Friendship cake is a rich slice of mid-twentieth-century baking culture, when neighbors literally passed sourdough starters back and forth in jars and the recipes that used them traveled with the starter. This prune cake version uses that fermented friendship bread starter as both leavening (the live yeast helps the cake rise) and flavor (the sourdough tang plays beautifully against sweet stewed prunes and cinnamon). Walnuts add crunch, and orange cream cheese icing finishes it as a proper sheet cake.

The technique notes are short. Make sure your friendship starter is warm and active before using. Cold or sluggish starter won’t lift the cake properly. Be gentle when folding the starter into the batter. Vigorous mixing knocks out the carbon dioxide that the wild yeasts have produced over days of fermentation. The stewed prunes (cooked, drained, chopped) bring caramelized sweetness and natural moisture that keeps the cake moist for days, the same reason banana bread stays good longer than vanilla cake.

Pro Tips

• Use a warm, recently-fed friendship starter. Inactive or cold starter won’t give the cake its characteristic rise and tang.
• Cook the prunes briefly in water until soft, then drain well. Leftover liquid waters down the batter.
• Chop prunes uniformly to about pea-size. Larger pieces sink to the bottom of the cake.
• Make ahead. Friendship prune cake actually tastes better on day two as the flavors meld.

Variations

• The recipe author suggests substituting dates for the prunes for a sweeter, slightly chewier cake.
• Bake as cupcakes for 25 minutes instead. The recipe makes about 2½ dozen.
• Top with a powdered sugar glaze instead of cream cheese frosting for a less rich finish.