Trim the crusts if desired and cut the bread slices into even, bite-sized cubes so they cook and absorb the masala uniformly.

Finely dice the onion and tomato, and slit the green chilies lengthwise, keeping everything ready before you start cooking.

Heat oil in a kadai over medium heat, add the mustard seeds, and let them sputter fully before adding the curry leaves.

Add the diced onion and slit green chilies to the tempering and sauté, stirring frequently, until the onions turn soft and translucent.

Add the diced tomato and turmeric, and cook, mashing lightly with the spatula, until the tomato breaks down into a soft, pulpy mixture.

Stir in the salt and mix well, tasting the masala base so the seasoning is balanced before the bread goes in.

Sprinkle in a small splash of water, cover the kadai, and let the masala simmer briefly so the flavors come together into a moist base.

Add the bread cubes to the kadai and gently fold them into the masala, tossing carefully so each piece is coated without turning mushy.

Turn off the heat, cover the kadai, and let the upma rest briefly so the bread finishes soaking up the masala evenly, then garnish with coriander leaves and serve hot.