Wash the turkey breast and pat dry. Rub with oil, salt and pepper. Place on the fat pan of the oven. Roast in the preheated oven (electric cooker: 200 °C / convection oven: 175 °C / gas: level 3) for approx. 1 1/4 hours
In the meantime peel and halve the onions. After 30 minutes spread around the roast. Add approx. 3/8 l hot water bit by bit
Wash and peel the asparagus and cut off the woody ends. Halve the asparagus. Peel and wash the carrots and cut them in half lengthwise. Cut the remaining zucchini slice (starter) into long, thin strips
Boil 1/2 l water with some salt and sugar. Cover the carrots and asparagus and cook for 15-20 minutes. Add zucchini in the last 2 minutes. Lift out the vegetables and keep warm
Put 1/8 l vegetable water into a pot. Stir in sauce powder, bring to the boil. Stir in butter bit by bit at low heat. Season to taste with orange juice and horseradish
Arrange the roast, vegetables and orange-hollandaise sauce. Garnish with chervil and orange slices if desired. Season the roast stock and serve extra. Boiled potatoes taste good with it