Line a 12-hole muffin tray with paper cases and set aside until needed.
Sift the plain flour and bicarbonate soda into a large bowl.
Add the caster sugar, cocoa powder, salt and chocolate chips and stir together.
Create a well in the centre of the dry mixture.
In a separate bowl, lightly beat the eggs before adding the sour cream, vegetable oil, milk and vanilla extract and whisk together until well combined.
Pour the liquid ingredients into the well in the dry ingredients, and very gently fold the mixture together. The batter should be slightly lumpy; do not over-mix.
Spoon the mixture into the paper cases, filling ⅔ to the top.
Bake for 20-25 minutes, use a skewer to check at 20 minutes - see notes.
Allow to cool in the baking tray for 5 minutes before transferring to a wire rack to cool completely.
Thermomix Method
Preheat oven to 180 degrees Celsius (fan-forced).
Line a 12-hole muffin tray with paper cases and set aside until needed.
Place the plain flour, bicarbonate of soda and cocoa powder into the Thermomix bowl and mix for 5 seconds, Speed 8.
Add the caster sugar, salt, eggs, sour cream, vegetable oil, milk and vanilla extract and mix for 5 seconds, Speed 5. Scrape down the sides of the bowl and repeat for a further 5 seconds, Speed 5. The batter should be slightly lumpy.
Use the spatula to gently fold the milk chocolate chips through the muffin batter; do not over-mix.
Spoon the mixture into the paper cases, filling ⅔ to the top.
Bake for 20-25 minutes, using a skewer to check at 20 minutes - see notes.
Allow to cool in the baking tray for 5 minutes before transferring to a wire rack to cool completely.
Notes
RECIPES NOTES & TIPS
Be careful not to overmix the batter - the dry ingredients (including the chocolate chips) are all stirred together first, to ensure everything is combined so that you won’t need to mix the batter too much when the wet and dry ingredients come together. Gently fold the batter together until it JUST comes together. A few little flour pockets won’t matter, but overmixing will result in tough, dense muffins.
Use an ice cream scoop to fill the muffin trays, if you have one. It helps to make lovely, rounded muffins.
Don’t overfill the muffin trays! Be careful not to fill them more than ⅔ full, or they will spill out over the top of the tray while baking.
How to tell if muffins are ready? - start to check the muffins at around 20 minutes. When a skewer or toothpick inserted into the middle of a muffin comes out clean, it is ready! Be careful not to mistake melted chocolate chips for raw batter.
Which type of chocolate is best? Dark (semi-sweet), milk or white chocolate chips can be used. Baking chocolate is recommended, because it has a strong, bold chocolate flavour that is perfect for adding to baked goods. But make sure it is a brand of chocolate that you know and LOVE for the very best results.
Storage - muffins are ultimately the best on the day they are made, but they can be stored in an airtight container at room temperature for up to 3 days.
Freezing - muffins can be frozen for up to 3 months in a good quality, airtight container. Thaw them overnight in the fridge, leave out at room temperature for an hour or heat them in the microwave.