Clean broccoli and cauliflower, wash and cut into florets. Peel, wash and slice the carrots. Cook cauliflower and carrots in boiling salted water for 8-10 minutes, add broccoli after 4-5 minutes. Wash fish, dab dry, season with salt, pepper and lemon juice. Grease a casserole dish. Place the fish in it and sprinkle with thyme.
Drain the vegetables and spread on the fish. Sprinkle with cheese and hazelnuts. Cook in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 15-20 minutes. Cover in between if necessary. Garnish casserole with thyme