Buttermilk (Best Option)
1 cup buttermilk per 1 cup whole milkButtermilk contains lactic acid which reacts with baking soda or baking powder in doughnut recipes, promoting leavening and a tender crumb. Its fat content is close to that of whole milk, preserving moisture and richness.
When using buttermilk, reduce or eliminate additional acidic ingredients to maintain balance. Stir gently to avoid overworking the dough.
Doughnuts made with buttermilk tend to be softer, with a subtle tang that complements the sweetness, while maintaining a light texture similar to those made with whole milk.