Mix egg yolk, buttermilk and butter. Mix dry ingredients and add to buttermilk mixture.
Beat egg white until stiff, then carefully fold into batter, taking care to retain volume.
Put about 1/2 tablespoon of a solid oil, such as Crisco, in the bottom of each aebleskiver pan cup and heat until hot.
Fill each cup level with batter. As soon as they get bubbly around the edge and golden underneath, turn them so the cooked half-sphere is on top (Danish cooks traditionally used a long knitting needle, but a fondue fork works very well also).
Continue cooking until cooked through, adjusting the heat and turning the ball to keep it from burning.
Notes
Makes about 14 Aebleskivers and serves 3-4 (I usually double or triple the recipe)
I am not a health professional and nutrition data is calculated programatically. Accuracy may vary with product selection, calculator accuracy, etc. Consult a professional for the best information.