In a small bowl, dissolve the active dry yeast and sugar in 1/2 cup (120 ml) of the warm water. Let it sit for about 10 minutes until frothy.
In a large mixing bowl, combine the all-purpose flour, whole wheat flour, and salt.
Add the yeast mixture, the remaining warm water, and the plain yogurt to the flour mixture. Mix well to form a smooth batter.
Cover the bowl with a clean cloth and let it sit in a warm place for about 2 hours to ferment and rise.
After the batter has fermented, stir in the baking powder.
Heat a non-stick skillet or a griddle over medium heat and lightly grease it with vegetable oil.
Pour a ladleful of batter onto the skillet, spreading it out to form a thin pancake about 8 inches (20 cm) in diameter.
Cook for about 2-3 minutes until bubbles form on the surface and the edges start to lift from the skillet. Do not flip the lahoh; it is cooked on one side only.
Remove the lahoh from the skillet and place it on a plate.
Repeat with the remaining batter, greasing the skillet lightly as needed.
Enjoy your meal!