Parboil the potatoes on steam mode for 10 minutes.. Put the duck fat for the roast potatoes into an enamelled GN container and leave to melt for 1 minute in hot combi oven. Add the potatoes to the GN container of hot duck fat, then sprinkle over the garlic cloves, thyme and salt and mix until the potatoes are well coated in the fat. Return the GN container to the oven and roast for 30 minutes, or until golden and crunchy.