In a large 8-quart stockpot, melt the ghee or butter over moderately low heat.
Add the chopped carrots, celery, potato, and turnip.
Sauté slowly, stirring occasionally, for 15 minutes to release their natural sweetness.
Stir in the water, bay leaf, all spices (coriander, cumin, peppercorns, cloves), ginger, salt, and tomatoes. Increase the heat to high and bring the mixture to a full boil.
Immediately reduce the heat to low, partially cover the pot, and maintain a gentle simmer for 1 hour and 15 minutes.
Strain the liquid through a fine-mesh sieve, discarding the solids. Use immediately, or cool completely to store.
Don't rush the initial sauté.
Letting the vegetables sweat and caramelize for the full 15 minutes is key to building a deep, rich flavor base.