Fill the bottom of a steamer, or base of a couscoussier should you possess one, with water and bring to a boil. When it looks like it's almost ready to boil, fill the kettle and put it on, then empty the couscous into a glass bowl, add the salt, crush in the cardamom
and mix with your fingers, then pour over a quart of boiling water from the kettle and place a plate on top of the bowl. Leave to stand for 5 minutes, then drain
and empty into the steamer or couscoussier top and sit this on top of the boiling water beneath. Add the slices of butter on top of the couscous
then clamp on the lid and let steam for about 7 to 10 minutes, by which time the couscous should be tenderly cooked and the butter melting. (You can do this a simpler way if you prefer, by just steeping the couscous in the boiling water for 10 to 15 minutes, but the grains will be more dense and more likely to clump. It's not disastrous, however, and you must decide what you're prepared to do.)
Meanwhile, toast the almonds by frying them in a dry pan until fragrant and golden, remove them to a plate, then do the same to the pine nuts. Chop the pistachios. Once the couscous is cooked, tip the bowl, fork through (and always use a fork for mixing or fluffing up couscous; a spoon will crush
it and turn it stodgy), sprinkling in the almonds and pine nuts
as you do so (and taste for seasoning at the same time, too). Now fork in most of the pistachios, and sprinkle those that remain lightly on top.