Place eggplant in a colander, sprinkle with coarse salt, and let stand for 30 minutes to sweat. Pat dry with paper towels.

Place mustard seeds in a small, dry saute pan and cook over moderate heat until they turn gray and start popping. Remove from heat and reserve.

Heat 1/4 cup clarified butter in a large skillet over moderate heat. Saute eggplant, stirring occasionally, until soft and golden. Remove from heat and reserve in a bowl with mustard seeds.

Heat remaining butter in a medium saucepan over medium high heat. Add onions and salt. Saute until onions are golden and soft. Add garlic and ginger, cook just until aromas are released, then stir in all spices. Cook an additional minute, stirring constantly to blend spices and prevent scorching.

Add tomatoes, water, and sugar. Turn heat to high and bring to a boil. Add spinach, bring back to a boil, and stir in eggplant mixture. When eggplant is heated through, about 2 minutes, remove from heat and serve.