In a large mixing bowl, whisk together the dry ingredients: flour, sugar, baking powder, baking soda, and salt. This ensures that the leavening agents are evenly distributed throughout the batter.

In another bowl, combine the wet ingredients: buttermilk, milk, melted butter, eggs, and vanilla extract. Whisk until well combined.

Pour the wet ingredients into the dry ingredients. Gently fold the mixture with a spatula until just combined. Be careful not to overmix; a few lumps are okay.

Gently fold in the fresh blueberries, ensuring they are evenly distributed without breaking them.

Preheat your waffle maker according to the manufacturer's instructions. This is crucial for achieving crispy, golden-brown waffles.

Once preheated, lightly grease the waffle maker with cooking spray or a small amount of melted butter to prevent sticking.

Pour the appropriate amount of batter onto the center of the waffle maker (usually about ½ to ¾ cup, depending on the size of your waffle maker). Close the lid and cook according to the manufacturer's instructions, typically around 4-5 minutes, until the waffles are golden brown.

Carefully remove the waffles using a spatula and serve immediately with your favorite toppings, such as maple syrup, whipped cream, or additional blueberries.