Preheat your oven to 200°C (180°C fan) and line a 12-hole muffin tin with paper cases. I like to give the cases a quick spritz of cooking spray on the inside — this stops the muffins from sticking and makes clean-up even easier. The oven should be fully hot before the batter goes in; you'll hear the fan settle into a steady hum.

In a large mixing bowl, whisk together the flour, caster sugar, baking powder, bicarbonate of soda, and salt. Use a fork or a small whisk to break up any lumps — you should see a pale, sandy-coloured mixture with no visible clumps of baking powder. This dry mix is your base for a tender, evenly risen muffin.

In a separate jug or small bowl, beat the eggs, then stir in the vegetable oil, buttermilk, and vanilla extract. Whisk until the mixture is a pale, creamy yellow and completely combined — you'll see tiny bubbles on the surface from the buttermilk reacting with the egg. This wet mixture should look smooth and glossy.

Pour the wet ingredients into the dry ingredients and stir gently with a wooden spoon or rubber spatula. Stop stirring as soon as you see no more streaks of dry flour — the batter will look slightly lumpy and thick, like a very rough cake batter. Overmixing at this stage will make the muffins tough and dense, so a few small lumps are absolutely fine.

Fold in the raspberries and white chocolate chips with just three or four gentle turns of the spatula. You should see the raspberries start to bleed slightly into the batter, creating delicate pink ribbons — this is exactly what you want. The white chocolate chips should be evenly distributed but not crushed; you'll see pale white flecks against the pink-streaked batter.

Divide the batter evenly among the 12 muffin cases, filling each one almost to the top — about three-quarters full is perfect. The batter should be thick enough that it doesn't run flat; it will hold a slight dome shape. Sprinkle a pinch of demerara sugar over each muffin for a crunchy, golden top if you like.

Bake for 18-20 minutes, or until the muffins are golden brown and a skewer inserted into the centre of a muffin comes out clean or with just a few moist crumbs. The tops should be domed and spring back when you gently press them with your fingertip. The kitchen will smell of sweet vanilla and toasted sugar — a sign that they're nearly ready. Let them cool in the tin for 5 minutes, then transfer to a wire rack.