Dissolve 1/2 teaspoon sugar and yeast in warm water in a large bowl; let stand 5 minutes. Add buttermilk, oil, and egg; stir with a whisk until smooth. Combine flours, 1 tablespoon sugar, baking powder, baking soda, and salt; stir well. Add to yeast mixture; stir until smooth. Cover and chill 8 hours.
Beat egg whites at high speed of a mixer until stiff peaks form. Gently fold egg whites into batter. Spoon about 1 tablespoon batter for each pancake onto a hot nonstick griddle or nonstick skillet. Turn pancakes when tops are covered with bubbles and edges look cooked.
Divide salmon strips evenly among pancakes, and top each with about 1 teaspoon Dilled Onion Compote. Garnish with dill sprigs, if desired.