Pre-heat the oven to 180º. Place the walnuts for no more than 8 minutes. Reserve.
In a large pan, heat a nob of butter with olive oil. Add the shalot and celery and leave for a couple of minutes to sweat.
Add half of the leek. After, add the rice to the pan and then the wine. Leave the wine to evaporate completely. Season to taste.
Add a large scoop of broth to the rice and stir it gently. When most of the liquid is evaporated, repeat the process.
Keep doing this until the rice is fully cooked. It should still be nice and crispy and not soggy.
Once done, toss the remaining leeks into the mixture, as well as the cheese in tiny chunks. Rectify seasoning if needed.
Remove from the heat and leave to rest for a couple of minutes.
Serve immediately, with the chopped walnuts and herbs on top.