Wash the potatoes and cook in boiling water until tender, then drain.
Peel the lower ends of the asparagus and trim off the woody ends. Cut any long stalks in half. Cook the asparagus in boiling salted water for 5 minutes, then add the peas and simmer for a further 2 minutes.
Drain the asparagus and peas, cool under cold running water and drain well. Peel the carrots and remove the stalks. Blanch the carrots in boiling water for 5 minutes until just tender, rinse in cold water then drain.
Clean the mushrooms with a cloth. Heat the oil in a large pan and sauté the mushrooms, stirring occasionally.
Remove the mushrooms from the pan and pour in the wine and stock. Bubble, scraping the base of the pan to loosen any juices. Pass the stock through a fine sieve.
Top up the liquid with orange juice to 500ml. Peel and finely chop the shallot. Melt the butter in a pan and saute the shallots. Add the flour and cook, stirring, until golden. Season with salt, curry powder and turmeric. Gradually add the stock, stirring well, to make a smooth sauce. Bring to the boil, stirring, and simmer for 10 minutes.
Fold in the cream and season the sauce with nutmeg and pepper.
Mix in the pre-cooked vegetables and heat again briefly. Season with pepper and serve.