Bring a pot of salted water to the boil. Wash and trim the sprouts and add to the pot. Cook for 5 minutes or until just tender. Drain well and set aside.
Using the same pan, add the butter and cook over a medium heat until it turns nut brown in colour (don’t take your eyes off it as it will burn).
Immediately return the sprouts to the pan and stir to combine with the butter.
Grate the zest of half the orange directly over the sprouts and then scatter over the hazelnuts.