Mix all wet ingredients before adding the melted butter. This will give the melted butter time to cool and adding after mixing other wet ingredients prevents the heat of melted butter from cooking the egg white.
When mixing the wet and dry ingredients together you should always hand mix with a spoon just until moist. This will produce a light, moist muffin/bread. Over mixing or using a hand blender will make the muffins/bread dense. You can use a fork or wisk to mix the wet ingredients.
Add a cup blueberries, for a yummy twist.