Preheat your oven to 375°F (190°C). Line a muffin tin with paper liners or grease it lightly with cooking spray to prevent sticking.

In a large mixing bowl, whisk together the sifted flour, sugar, baking powder, baking soda, and salt until well combined. This helps to evenly distribute the leavening agents.

In another bowl, whisk together the buttermilk, vegetable oil, eggs, and vanilla extract until smooth. Mixing wet ingredients separately ensures that the eggs are fully incorporated.

Pour the wet ingredients into the dry ingredients. Gently fold them together using a rubber spatula until just combined. Be careful not to overmix, as this can lead to tough muffins.

Gently fold in the raspberries and white chocolate chips (if using) into the batter. This will help to distribute the fruit evenly without breaking them apart.

Spoon the batter into the prepared muffin tin, filling each cup about 2/3 full. This allows room for the muffins to rise.

Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean. This ensures that the muffins are fully cooked.

Remove the muffins from the oven and let them cool in the tin for 5 minutes. Then transfer them to a cooling rack to cool completely. Enjoy your raspberry muffins warm or at room temperature!