Whisk together the dry ingredients in a large bowl. In a separate bowl, whisk the eggs, then whisk in the milk, and buttermilk. Pour the wet ingredients into the dry ingredients and combine, using a wooden spoon. Mix only until the batter just comes together. Stir in the melted butter. Do not over-mix! The mixture should be a little lumpy. Lumpy is good. Lumpy batter means fluffy pancakes. Fold in the blueberries (or wait to add them once the batter has already been poured on the griddle - this will keep them from bleeding).
Heat a flat cast iron surface—griddle or large pan—to medium heat. Oil the pan with either a little butter or vegetable oil. Ladle the pancake batter onto the griddle to the desired size (a quarter-cup measure works well for this), anywhere from 4 to 6 inches wide. When air bubbles start to bubble up to the surface at the center of the pancakes (about 2-3 minutes), use a flat metal spatula to flip them over. After a minute, peak under one for doneness. When golden or darker golden brown, they are done. Note that cooking the second side takes only about half as long as the first side. And the second side doesn't brown as evenly as the first side. Continue to make the batches of pancakes, putting a little oil or butter on the pan before each batch so the pancakes don't stick.
Serve immediately. Serve with butter and maple syrup.