In a large mixing bowl, whisk in flour, baking powder, salt, and preferred optional mix-ins. If adding a solid fat, cut or massage in butter or shortening using your fingers or pastry cutter.
Heat 1 cup of milk or water in the microwave (~45 seconds or so) or on the stove until the temperature 100˚F-110˚F / 38˚C-43˚C. With a spoon, slowly stir the liquid in with the other ingredients. Begin kneading with your hands until all the flour is well moistened and begins to form a ball. If necessary, add milk (water) or flour to adjust the texture.
Preheat the oven to 410°F / 210°C.
Scoop the dough out onto a lightly floured surface. Knead, fold, and turn it over just enough to create a smooth round ball. Kneading the dough too much will create a heavy and dense bread.
Once the oven has preheated, place a cast iron skillet (~9 inches in diameter works well) or Dutch oven in the oven on the middle rack for 5 minutes to heat up. After 5 minutes, remove the skillet and dust the bottom of it with flour to prevent the dough from sticking.
Place the dough round in the skillet and flatten the dough to near the edges.
Put the skillet in the oven for about 45 minutes or until the top is lightly browned. The bread will swell during baking.
Shake the skillet after 15 minutes of baking to ensure even browning and to prevent sticking.
The bread is baked when a knife inserted in the center of it comes out clean or the internal temperature reaches 190˚F / 88˚C. The bread should offer a hollow sound when tapped in the center.
Let the damper sit for 5 to 10 minutes before cutting and serving.