Grind the mustard seeds in the universal grinder. Mix mustard seeds and maple syrup and season with salt
Wash the meat, dab dry and rub thickly all around with mustard paste. Roast in a roaster in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for 2 1/2 - 3 hours
Clean the leek, cut into pieces of about 4 cm and wash. Wash the thyme, shake dry. Peel and wash the potatoes and cut them into halves or quarters depending on their size. Wash and quarter apples, remove core and halve apple pieces. Prepared ingredients, except for some thyme for garnishing, season with salt and pepper and spread around the roast about 45 minutes before the end of the frying time. Pour on broth
Remove the finished roast and let it rest for a short time. Cut into slices and garnish with thyme
Put in a cool place for about 2 hours. Whip the cream until stiff. Gradually add the sugar. Remove the cake from the edge of the springform pan. Dust the surface evenly with cocoa. Pour the cream into a piping bag with a star-shaped spout and decorate the cake with cream tuffs.