Heat the oil in a non-stick frying pan. Fry the meat in batches for approx. 3 mins. Remove, season, reduce the heat, add a little oil if needed. Sauté the garlic and shallots for approx. 2 mins. Add the vegetables and tomato purée, cook for about another 5 mins. Pour in the wine and reduce almost completely. Pour in the stock, return the meat to the pan, simmer for approx. 15 mins. Divide the sauce into the prepared dishes.
Sweet potato mash
Place a steamer basket in a wide pan, fill with water to just below the bottom of the basket. Add the sweet potatoes, season with salt, cover and cook over a medium heat for approx. 15 mins. until just soft. Remove, drain, pass the potatoes through a food mill. Stir in the butter and cheese, transfer to a piping bag with a serrated nozzle. Spread over the sauce, scatter over the thyme.
Approx. 20 mins. in the centre of an oven preheated to 200°C.