Peel the asparagus, place in a buttered roasting pan, sprinkle with the sliced orange (leave the peel on), sprinkle with the herbs, sprinkle with salt and sugar. Close the roaster well and put it in the oven preheated to 200 degrees. After a quarter of an hour you can add about 150 ml of water. Cook for 50 minutes.
In the meantime, cook the potatoes.
Sauce:
Heat 300 ml poultry stock (glass) with 100 g mascarpone and stir until creamy. Season with salt and pepper, add the juice and the grated zest of a lime and whip with the hand blender until frothy before serving.