Wash the potatoes and cook in boiling salted water for 15-20 minutes, then rinse with cold water and peel. Wash the asparagus and cut off the woody ends. Peel the white asparagus. Put the asparagus peels in 1/2 litre boiling salted water. Leave to simmer on a low heat for about 30 minutes.
In the meantime cut the asparagus into bite-sized pieces. Clean and wash the mushrooms. Drain the asparagus peelings and catch the stock. Cook the asparagus pieces in the stock for approx. 12 minutes, then set aside. Sauté the mushrooms in hot fat for 5 minutes, turning. Season with salt and pepper. Deglaze with the asparagus stock and cook for another 5 minutes. Stir in sauce powder. Heat the asparagus and potatoes in it. Stir in cream.
Season with salt and pepper. Deglaze with the asparagus stock and cook for another 5 minutes. Stir in sauce powder. Heat the asparagus and potatoes in it. Stir in cream. Season again with salt, pepper and white wine. Serve ragout garnished with ham and parsley