Place pumpkin in a sauce pan and cover with water. Add the butter and a tsp of salt. Bring water to the boil and cook the pumpkin until soft. Drain well and put to one side. bring 300ml (10fl oz) of water to the boil in a large saucepan. Once water is boiling, add a tsp of salt, 200ml (6.6fl oz) of double cream and the miele meal. Stir with a whisk while cooking. Add the grated Parmesan and the shredded sage. Once the mieli meal is cooked, remove from the heat and keep covered. For the pinotage sauce, sweat the chopped onion in a little olive oil. Once translucent, add the wine and cook until reduced by half. Add the demi glace and cook for a couple more minutes. Add the mushrooms and continue cooking for another 2-3 minutes. Check the sauce for seasoning, adding salt and pepper to taste. Heat a ribbed pan until almost smoking. Once hot, put the whole loin in the pan, turning after about 2 minutes. Cook until ready - approx 4 minutes for rare to med, 8 to 10 minutes for meduim well. Remove the meat from the pan once cooked and allow to rest for a few minutes before serving. Mix the cooked pumpkin into the mielie meal, heat gently and check for seasoning, adding salt and pepper to taste. Spoon the mielie meal onto a dinner plate. Slice the meat and arrange on the plate with the mielie meal. Finally, spoon the mushroom and wine sauce around the meat and the mielie meal and serve.