Sift the flour and baking powder over a bowl, and then set aside.
Beat the egg in a mixing bowl. Mix in the brown sugar, and then add 1 1/4 cups milk, the vanilla, and salt.
Stir in the sifted flour mixture until just moistened. If the batter seems too thick at this point, slowly add the remaining amount of milk until the batter is thick but pourable. If you like a thicker pancake, keep the batter on the thicker side. Gently fold in the blueberries or chocolate chips, if using. (Conversely, you may evenly distribute them over the batter while cooking.)
Preheat a heavy-bottomed skillet over medium heat. (I love a cast iron skillet for this.) Add a couple teaspoons of oil, just enough to coat the bottom of the pan. Pour approximately 1/4 cup of the batter into the pan for each pancake. Cook until beginning to bubble, about 1 1/2 minutes. Flip, and continue cooking until golden brown, adjusting your heat as necessary (I often have to reduce the heat to medium-low after the first few pancakes) and adding an extra teaspoon or so of oil with each batch.
Serve with maple syrup or toppings of choice. Any leftovers may be refrigerated or frozen. I like to reheat in the toaster oven until just warm. If you would like to keep the pancakes warm until serving, place them in a 200-degree oven while cooking the rest.