Whisk buttermilk, butter, and egg together in bowl until blended. Combine flours, soda, and salt in another bowl. Whisk buttermilk mixture into dry ingredients until just blended.

Heat large nonstick skillet or griddle over medium-high heat. Grease lightly with vegetable cooking spray. For each pancake, spoon scant 1/4 cup of the batter into skillet, spreading batter lightly with back of spoon. Cook until bubbles form on surface of pancakes, about 2 minutes. Turn pancakes over and cook 1 to 2 minutes more. Repeat with remaining batter. Serve with maple syrup. Makes 12 pancakes.

To make 1-1/4 cups sour milk, place 4 teaspoons lemon juice or vinegar in a 2-cup glass measuring cup. Add enough milk to make 1-1/4 cups liquid; stir. Let the mixture stand for 5 minutes before using it in a recipe.