Pre heat oven to 215°C / 420°F / 195°C fan-forced see notes and line a 12 hole muffin pan with cupcake papers
In a large mixing bowl, whisk together the cooled melted butter and sugar
Whisk in the eggs, then the buttermilk, yogurt and vanilla
Reserve a tablespoon of flour, then sift the rest, along with the baking powder, baking soda, nutmeg and salt
Fold the sifted ingredients into the wet ingredients until almost combined
Toss the chocolate chips in the reserved flour, then very lightly fold them through the mixture (be careful not to overmix)
Using a large ice cream scoop, place heaped scoops of mixture into the lined muffin pan
Sprinkle the muffins with raw sugar
Bake at 215°C for 7 minutes, then reduce the temperature to 180°C /350°F or 160°C fan-forced and bake for another 20 minutes
Remove from the oven, rest muffins in the pan for 10 minutes, then remove them from the pan, onto a cake rack (or just eat them now!)
Muffins are best eaten on the day, but will keep for a couple of days in an airtight container