Pre-heat oven to 200◦c. Stand veal rack up in a flameproof roasting pan. Drizzle with 1 tbsp of oil and season well. Roast for 45 minutes. Add apples to roasting pan, turning to coat with pan juices. Cook for a further 15 minutes for medium-rare veal and until apples are lightly golden. Transfer veal and apples to a large plate and cover loosely with foil.
Finely chop enough sage leaves for 1 tbsp and set aside. Add remaining oil in a frying pan over medium heat. Add remaining sage leaves, 3-4 at a time, cooking for 40 seconds or until leaves are crisp. Set aside on paper towel.
Drain pan juices from roasting pan, leaving 2 tsp. Combine butter and flour in a small bowl. Using fingers mix together until a thick paste forms. Set aside. Put roasting pan over a medium heat. When hot, add redcurrant jelly and apple juice, whisking until melted and combined. Add butter paste, a little at a time, stirring well until melted and well combined. Add reserved chopped sage leaves and mustard, season and stir until combined. Strain through a fine sieve. Arrange veal and apples on a platter. Sprinkle fried sage leaves over platter. Serve with gravy on the side and roast pumpkin, potatoes and green beans.
If redcurrant jelly is unavailable you could use granberry or quince jelly instead