Season the lamb with salt and pepper. In a bowl, combine the flour with the Essence. Dust the lamb with the seasoned flour, shaking to remove any excess. In a large saute pan or Dutch oven, heat the oil and melt the butter over medium-high heat. Add the meat in batches and cook, turning, until browned on all sides. Remove with a slotted spoon.
To the fat in the pan, add the onions, leeks, and carrots, and cook, stirring, until softened, about 4 minutes. Add the tomato paste and cook for 1 minute. Add the wine and stock. Bring to a boil, stirring to deglaze the bottom of the pan. Return the meat to the pot and add the bay leaves and thyme. Lower the heat to a simmer, cover, and cook, stirring occasionally and skimming any fat that forms on the surface, until the meat is very tender, 1 1/2 to 2 hours.
To make the Kumara: In a medium saucepan, combine the kumara and salt and cover with water by 1-inch. Bring to a boil and cook until fork tender, about 10 minutes. Drain and return the kumara to the saucepan and over low heat, mash with a potato masher or heavy whisk. Add the butter, sugar, ginger, and white pepper, and mash into the potatoes.
Remove the lamb from the heat and discard the bay leaves and thyme sprigs. Adjust the seasoning, to taste. Serve over the mashed kumara or sweet potatoes. Garnish with chopped parsley and serve.
Yield: 4 servings