Preheat your waffle iron, according to manufacturer's instructions
Melt the 4 tablespoons of butter in the microwave or on the stove top, whichever works best for you.
In a medium bowl, combine the two kinds of flour, salt, sugar and baking soda. Mix until evenly combined.
If using milk: Pour the 1 and 3/4 cups milk into a 2-cup measuring cup. Add 1 tablespoon vinegar. The milk will curdle; this is the goal. (You can also do this using measuring cups and a small bowl, but this method saves on dishes.)
If using buttermilk: add the 1 and 3/4 cups of buttermilk into a 2-cup measuring cup. (You can also do this using measuring cups and a small bowl, but this method saves on dishes.)
Next, crack the 2 eggs into the 2-cup measuring cup and use a fork to beat them together with the milk/buttermilk.
Add the wet mixture to the dry mixture and mix to combine. Don't worry if some lumps remain.
Following the instructions for your waffle iron, ladle batter into the iron and cook. My iron cooks waffles in about 3 and a half minutes, but yours will likely vary.
Serve and enjoy! If you're not serving the waffles immediately or waiting for the entire batch to be done before eating them, keep the waffles warm in an oven on low heat.