For making upma, first dry roast semolina over medium heat in a heavy bottom pan for 5 - 6 minutes. Stir continuously at regular intervals while roasting. Transfer to a plate and set aside till required. If you are using readymade roasted semolina then skip this step.
Heat oil in the wok or kadhai over medium flame. Add mustard seeds, cumin seeds, urad dal, chana dal, peanuts, curry leaves, asafoetida and fry for 1 - 2 minutes. The colors of lentils and peanuts will change to light brown.
Next, add sliced cashews, grated ginger, green chili and fry for 1 - 2 minutes or till cashews turn light golden in color.
Add the chopped onion and fry for 3 - 5 minutes or till onion start turning translucent.
Add peas, salt, crushed pepper and stir to combine. Next, add water, stir to combine and increase the flame to high. Let the water start boiling. Taste and adjust the seasoning.
Slowly add the roasted semolina with a steady flow and stir continuously from the other hand in a circular motion to avoid any lumps. Keep stirring until semolina absorbs all the water. Cover the wok with a lid and cook over low heat for 3 - 5 minutes.
After 3 - 5 minutes, turn off the heat. Open the lid and fluff the upma using a fork. Drizzle a teaspoon of ghee and garnish with chopped coriander.
Serve rava upma warm with coconut chutney or sambar.