Preheat the oven to 200C/400F/Gas 6. Line a 12-hole muffin pan with muffin cases, then set aside.
Whisk together the flour, baking powder, and salt. Set aside.
In a large bowl, whisk together the eggs and sugar until thick and light in colour. Add the buttermilk, oil, and vanilla, and whisk until combined.
Add the dry ingredients in thirds and fold in until just combined - do not overmix. Fold in the chocolate chips. The mixture will be thick and somewhat lumpy.
Spoon the mixture into the prepared pan (filling to the tops), and bake for 15 - 20 minutes, or until a toothpick inserted into the centre comes out clean.
Allow to cool for 5 - 10 minutes in the pan before transferring them to a wire rack to cool completely.
Video
Notes
*To make your own buttermilk, simply add 1 tablespoon of fresh lemon juice or white vinegar to 1 cup (240ml) of milk. Stir to combine, and allow to sit for 5 - 10 minutes until slightly thickened and curdled.Muffins stay fresh in an airtight container at room temperature for up to 5 days. They also freeze well for up to 2 months. Thaw overnight in the fridge.