Preheat a fan-forced oven to 140°C / 275°F or a conventional oven to160°C / 320°F. Line two cupcake tins with the cupcake liners.
Add the flour, sugar, baking powder and salt to a large mixing bowl and mix with a hand mixer until well combined.
Next, add the softened butter and mix on low speed until the mixture reaches a crumbly, sand-like texture.
Add the eggs, milk, oil, yoghurt, blue food gel, purple food gel, boysenberry flavouring and vanilla, and mix on low speed until all the dry ingredients are incorporated. Scrape down the side of the bowl and mix for a final 20 seconds. It’s at this point that you can add any flavourings or food-gel colourings to the batter.
Fill each liner three-quarters of the way. Using an ice-cream scoop to transfer the batter to the cupcake liners makes this a quick and easy process, and ensures each liner contains exactly the same amount of batter and that the cupcakes will bake evenly. Bake for 40–50 minutes, or until a toothpick inserted in the middle of a cupcake comes out clean. Allow the cupcakes to cool completely on a wire rack before frosting.