2.Heat ghee in large saucepan; cook onion, garlic and ginger, stirring, until onion softens. Add nuts, seeds and paste; cook, stirring, until fragrant.
3.Add cream and mushrooms; simmer, covered, 15 minutes. Add spinach; cook, stirring, until wilted. Serve curry with yoghurt.
Kalonji seeds are also known as nigella or black onion seeds. Tiny, angular seeds, black on the outside and creamy within, with a sharp nutty flavour that can be enhanced by frying briefly in a dry hot pan before use. Kalonji can be found in most Asian and Middle-Eastern food shops.