Preheat oven to 180 degrees celsius (fan-forced). Line 2 X 12-hole muffin trays with liners and set aside.
Place the four, baking powder, bi-carb soda and salt into the Thermomix bowl and sift by pressing Turbo 5-10 times. Set aside in a separate bowl.
Place the butter, caster sugar and brown sugar into the Thermomix bowl and cream for 30 seconds, Speed 4. Scrape down the sides and repeat for a further 20 seconds.
Reduce to Speed 3 and with the blades turning, add the eggs, one at a time, and continue to mix until well combined.
Add the mashed bananas, vanilla extract and greek yoghurt and mix on Speed 5, 20 seconds.
Add the reserved dry ingredients and mix on Speed 4, 5 seconds or until just combined. Add the chopped strawberries and gently fold through with a spatula.
Divide the mixture equally between the muffin holes (depending on the size of your muffin trays, this recipe will make anywhere from 12 very large to 24 small muffins).
Cook for 15-20 minutes or until the tops are golden. Remove from the oven and allow to cool in the trays for 5 minutes before transferring to a wire rack to cool completely.