Dice butter, melt in a metal bowl over a hot water bath, but do not stir. As soon as the whey has settled at the bottom, pour off the clarified butter from the top, allow to cool slightly (process takes 20-30 minutes)
In the meantime, wash and peel the asparagus and cut off the woody ends. Wash potatoes thoroughly, cook in boiling salted water for 20-25 minutes
Wash the meat, dab dry and tie into shape with kitchen string. Heat oil in a pan. Fry the meat for 4-5 minutes, season with salt and pepper, remove and place on a baking tray. Cook in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for 10-12 minutes in medium heat.
Cook the asparagus in plenty of boiling salted water with 2 teaspoons of sugar for 12-15 minutes. Wash the orange hot, rub dry, rub off the peel. Cut orange in half and squeeze, mix juice and peel with white wine. Peel shallots, dice finely, place in a pot with egg yolks and orange-wine mixture, season with a little salt, pepper and sugar, whip until frothy over a hot water bath. Gradually fold in clarified butter. Season sauce with sugar, salt, pepper and lemon juice
Remove the meat, wrap it in foil and let it rest in a warm place for about 5 minutes. Drain the potatoes. Take out asparagus, drain. Remove meat from foil, arrange on plates with asparagus and sauce, garnish with thyme