How to Make It
In a large saucepan, heat 3 tablespoons of the ghee. Add the onion, season with salt and pepper and cook over moderately low heat, stirring occasionally, until soft and golden brown, about 20 minutes. Add the garlic, chiles, ginger and fenugreek leaves and cook over moderate heat, stirring occasionally, until softened, about 5 minutes. In 3 batches, add the spinach and mustard greens, letting each batch wilt before adding more. Stir in the garam masala and season with salt and pepper. Scrape the greens into a medium bowl and let cool slightly. Wipe out the saucepan.
In a food processor, pulse half of the greens with half of the heavy cream until finely chopped. Return to the saucepan and repeat with the remaining greens and cream. Keep the saag warm over very low heat, stirring occasionally.
In a medium nonstick skillet, heat 1/2 tablespoon of the ghee until shimmering. Add half of the paneer and cook over moderate heat, turning once, until golden brown, about 5 minutes. Transfer to a paper towel–lined plate to drain. Repeat with the remaining ghee and paneer. Fold the paneer into the saag and cook over low heat until warmed through, 2 to 3 minutes; season with salt. Transfer to a bowl and drizzle with warm cream. Serve with steamed basmati rice.