Preheat oven to 160C fan forced or 180C convection oven
Cream butter and sugar until light and fluffy. Speed 3-4/3 mins. Scrape sides often
Add eggs one at a time
Add banana, mashed until mixed
Add creme fraiche, espresso shot and vanilla bean extract, slow speed (speed 2) until well blended
Lastly, add the dry ingredients (flour, bi carb soda and salt) and choc chips or nuts until JUST mixed.
Do not over mix
Put into muffin cups, fill 1/2 full and no more or it will spill over in the oven.
Depending on the size, cook until the middle is firm to touch or a skewer inserted into the middle comes out clean.