1
: In a large bowl, toss potatoes with oil, salt, pepper and thyme. Transfer to a parchment-lined baking sheet. Roast in a preheated 425ºF (210ºC) oven for 35 to 40 minutes, until cooked and golden brown. Turn occasionally, but carefully, not to break.
2
: Meanwhile, in a saucepan, to prepare gravy, melt butter in a saucepan over medium-high heat. Add mushrooms and cook for 4 minutes. Add flour, stir and cook for 3 minutes. Stir in milk and chicken stock, bring to a gentle boil, stirring. Reduce heat to medium and cook 5 minutes, until thickened (sauce is not really thick). Season with salt and pepper.
3
: To serve, mound potatoes on individual serving plates. Spoon over gravy and sprinkle with cheese. Serve hot.