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

2. In a large mixing bowl, sift together the flour, cocoa powder, baking powder, baking soda, salt, and sugar until well combined.

3. Add the chopped milk chocolate, dark chocolate, and white chocolate to the dry mix. This will help distribute the chocolate evenly throughout the muffins.

4. In a separate bowl, whisk together the eggs, buttermilk, vegetable oil, and vanilla extract until smooth.

5. Pour the wet ingredients into the dry ingredients and gently mix until just combined. Be careful not to overmix; it's okay if there are a few lumps.

6. Spoon the batter into the prepared muffin cups, filling each about 3/4 full. Before baking, add a few extra chocolate chunks on top of each muffin.

7. Bake in the preheated oven for 18-20 minutes or until a toothpick inserted into the center comes out clean.

8. Allow the muffins to cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely.