Preheat the oven to 200°C (392°F) or 180°C (356°F) for fan-forced. Place the muffin cases in the muffin tray and spray the inside of the cases generously with oil to prevent the muffins from sticking.
FOR THE WET INGREDIENTS - a medium bowl mix in the milk and the vinegar and leave to stand for 10 minutes or until the milk has thickened slightly. Add in the eggs, milk, sugar, vanilla and oil to the milk, mix well to combine.
FOR THE DRY INGREDIENTS - In a large bowl add the flours and sift in the baking soda and salt and mix well.
Make a well in the middle of the dry ingredients and pour in the wet ingredients, stir a few times only. Add in the chocolate and raspberries and stir a few more times just to combine, do not overmix the batter. It's okay if the batter is lumpy but make sure there are no patches of dry flour remaining.
Fill muffin cases no more than two thirds full with the batter. Bake in preheated oven for 18 to 20 minutes but check the muffins 2 to 3 minutes prior to prevent overcooking them. Muffins are ready when the skewer comes out clean when inserted in the middle. Take the muffins out of the tin and cool them on a baking rack.
Notes
NOTE 1: Raspberries - Frozen or fresh raspberries can be used in this recipe. If using frozen, don't take them out of the freezer until it's time to throw them in the batter as defrosted raspberries will disintegrate and colour the entire batter.NOTE 2: White chocolate - White, dark or milk chocolate will work wonderfully in this recipe as they all offer sweetness to balance off the tartness from the raspberries. Here it's common to use white chocolate chips.NOTE 3: Vinegar and milk - This is basically a quick and cheats way of making buttermilk if you don't have any available. If you do have buttermilk you can use this instead and leave out the vinegar and milk.Buttermilk and baking soda help the muffins rise nicely, it also makes them airy and fluffy.NOTE 4: Oil - Use oils with no flavour such as vegetable, canola, rice bran or light/mild virgin oil.NOTE 5: Flour - To make my muffins a little healthier and less processed I often mix in wholemeal flour to the plain flour. This makes the muffins slightly denser in texture so if you prefer a lighter muffin stick to plain flour.Storage - will last up to 3 days at room temperature in a container, or up to 3 months if frozen.