Peel and finely chop the onion. Heat half of the butter in a pan and sweat the onion in it until soft, then stir in the bulgur and sauté briefly. Pour in the broth, bring to a boil, cover and simmer for 10-15 minutes until the liquid is absorbed.
Meanwhile, clean the mushrooms and slice thinly.
Heat the olive oil in a pan. Cook the mushrooms until they are browned and slightly soft. Season with salt and pepper. Add the mushrooms and their juices to the bulgur. Stir everything together, cover and keep warm.
Toast the almonds and hazelnuts in a dry skillet until fragrant, then stir together with the remaining butter. Mix the nuts and parsley with the bulgur. Season to taste and serve.