In a medium bowl, whisk together all ingredients except 2 tablespoons butter until evenly combined and moistened thoroughly (some small lumps will remain). Set mixture aside to rest while griddle heats or cover and store in the refrigerator to rest up to 12 hours before using. (If batter rests, stir briefly before using.)
Heat a large seasoned cast iron skillet, frying pan, or griddle over medium heat. To check that the pan's properly heated, sprinkle a few drops of water on pan or griddle and water will "dance" around before evaporating.
Melt 1 tablespoon butter in pan. When it foams, ladle 1/4 cup batter for each pancake and cook until bubbles cover the top, about 3 minutes. Flip and cook until golden brown, another 1 minute. Repeat with remaining batter. Serve immediately topped with Blueberry Maple Syrup.
Blueberry Maple Syrup:
Combine 1 1/2 cups berries and syrup in a small saucepan over medium heat. Cook until berries are slightly softened, about 2 minutes, then mash using the back of a spoon. Simmer until mixture foams up a bit, about 1 to 2 minutes more.
Remove from heat, strain to remove blueberry solids, stir in remaining 1 1/2 cups berries, and use to top pancakes, waffles, or French toast.