Mix eggs into yogurt and stir in the melted butter or oil.
Gently fold the wet ingredients into the dry ingredients with a large spoon or spatula adding more yogurt (or milk) if necessary . Try not to over mix.
Spoon into 6 giant, or 12 medium greased muffin pans. Pans should be piled high with mixture.
Sprinkle tops with a little coffee crystals or other sugar if desired.
Bake for approximately 30 minutes (or until a skewer comes out clean) for large muffins less for smaller muffins.