Preheat oven to 180 C. Grease 12 cupmuffin pan or line with paper muffin cups.
Mix flour, baking powder, bicarbonate of soda and salt together in a bowl. In a separate bowl, beat together banana, sugar, egg and vanilla essence. Stir in creme fraiche. Stir into flour mixture until just combined. Spoon evenly into prepared muffin pans.
Bake in preheated oven for 15 to 20 minutes, or until a wooden skewer inserted into centre of a muffin comes out clean. Allow to cool before serving. For best flavour, place in an airtight container or plastic bag overnight.