Place a dry heavy-bottomed pan over medium-low heat. Add the semolina and roast, stirring frequently, for 5 to 7 minutes until it smells nutty and turns very lightly golden without browning. Transfer the semolina to a clean plate and set aside.

Bring 3 cups of water to a boil in a kettle or separate pot. Keep it hot and ready.

In the same pan, heat the cooking oil or ghee over medium heat. Add the mustard seeds and let them sputter. Add the chana dal, urad dal, and cashews, cooking for about 1 minute until the lentils turn light golden.

Add the sliced onions, minced ginger, slit green chilies, and curry leaves. Sauté for 3 to 4 minutes until the onions turn translucent. Add the mixed vegetables and cook for another 2 minutes.

Carefully pour the boiling water and salt into the pan. Stir well and let the water come to a rolling boil.

Reduce the heat to low. Slowly pour the roasted semolina in a thin stream while stirring continuously with a wooden spoon or whisk to prevent lumps from forming.

Once all the semolina is mixed in and has absorbed most of the liquid, cover the pan with a tight lid. Let it cook on the lowest heat setting for 3 to 4 minutes so the steam finishes cooking the grains.

Turn off the heat. Drizzle the optional teaspoon of ghee and top with chopped coriander leaves. Fluff the upma gently with a fork and serve warm.