Dry roast semolina until its aroma emanates. Halve the red chillies. Chop the green chillies fine. Peel and chop the ginger fine. Heat oil and ghee in a sauce pan, add mustard, urad dal, cashewnuts, red chillies and asafoetida. WHen the mustard crackles, add the green chillies, ginger and curry leaves and saute for a little and add salt. Add the semolina gradually to the boiling water, stirring the ingredients constantly to avoid lumps. Remove from fire when the semolina is done to a turn, water can be sprinkled until the semolina is done. If more water is added inadvertantly, the upma will turn mushy. Add lemon juiec, mix well and serve.