Heat a griddle or frying pan over medium heat.
In a large bowl, mix together the flour, baking powder, baking soda and salt. Set aside.
In another bowl, combine the sour cream, crème fraîche or yogurt, milk, beaten eggs and melted butter.
Add the wet ingredients to the dry ingredients all at once, stirring just until combined.
Lightly grease the griddle or frying pan.
Place dollops of batter (a scant quarter cup of batter makes a good size pancake) on a hot, lightly greased griddle or frying pan.
Cook on one side until bubbles form and break on the surface.
Turn the pancakes over with a spatula or egg flipper.
Cook for another minute or so until done.
Serve immediately.