Wash and peel the black salsifies. Place in vinegar water so that they do not discolour. Bring salt water to the boil. Cut the black salsifies into pieces and cook in them for about 20 minutes. Cook the rice in boiling salted water for 20 minutes.
Clean, wash and slice the leek. Add to the black salsify about 5 minutes before the end of the cooking time. Clean, wash and dry the mushrooms. Heat 1 tablespoon of fat in a saucepan. Brown the mushrooms in it and take them out.
Melt the remaining fat. Sweat flour and curry in it. Deglaze with 3/8 litres of vegetable water. Season to taste with salt and pepper. Drain the vegetables and add to the sauce with the mushrooms. Arrange rice and black salsify ragout together.
Garnish with parsley.