Preheat oven to 350°F.
Beat egg yolks, molasses, sugar and butter together until light.
Whisk or sift together dry ingredients until well mixed.
Add yogurt or sour cream, then the dry ingredients. Beat for 1 minute.
Bake in buttered or paper-lined muffin cups for about 20 minutes or until a toothpick inserted in the center of a muffin comes out clean.
Remove from oven and brush tops with butter; sprinkle lightly with coarse turbinado sugar, if desired.
Submitted by: CM