In a large mixing bowl, whisk together the all-purpose flour, baking powder, salt, and granulated sugar (if using) until well combined.
Make a well in the center of the dry ingredients and pour in the lukewarm water and vegetable oil or melted butter. Mix the wet ingredients into the dry ingredients until a soft dough forms.
Turn the dough out onto a lightly floured surface and knead it for about 5 minutes until smooth and elastic. You can also use a stand mixer with a dough hook attachment for kneading.
Shape the dough into a round loaf or individual rolls, depending on your preference. If making a loaf, place it in a greased and floured loaf pan. If making rolls, arrange them on a greased and floured baking sheet, leaving space between each roll for rising.
Cover the loaf pan or baking sheet with a clean kitchen towel and let the dough rise in a warm place for about 30-45 minutes, or until it has doubled in size.
While the dough is rising, prepare your steamer. If you have a steamer specifically designed for bread or a steamer basket, use that. Otherwise, you can use a large pot with a steamer insert or a colander placed in a pot with a little water at the bottom.
Once the dough has risen, place the steamer over medium heat and bring the water to a gentle boil.
Carefully transfer the risen dough to the steamer, either by sliding it from the loaf pan or by lifting the rolls onto the steamer insert or colander. Be cautious to avoid burning yourself with the steam.
Cover the steamer with a lid and steam the bread for about 30-40 minutes, or until the bread is cooked through and sounds hollow when tapped on the bottom. Check occasionally to ensure that there is enough water in the pot, adding more if necessary.
Once cooked, remove the bread from the steamer and let it cool on a wire rack before slicing or serving.
Steam Bread is a soft and fluffy bread that is popular in various cuisines around the world. It can be enjoyed with various spreads, used as a sandwich bread, or served alongside soups and stews.