Instructions

Heat the oven to 200°C/180°C fan/gas 6. Grab a wooden spoon and sit a potato in the bowl of the spoon. Starting at one end, cut across the potato widthways at 3mm intervals. The spoon will stop you cutting right through the potato. Carry on until you’ve sliced all the potatoes, putting them into a roasting tray as you go.
Mix the oil, rosemary, salt, pepper, lemon zest and crushed garlic in a small mixing bowl, then use a pastry brush to brush the mixture all over the potatoes, making sure you get down into the cuts. Once all the potatoes are coated, bake for 30-35 minutes or until golden (see tip).
While the potatoes are in the oven, whizz together the ‘cheese’ sauce ingredients in a blender or food processor until smooth, then pour into a small saucepan.
Heat the sauce over a low heat, stirring constantly, until it’s thick and creamy (see Make Ahead).
When the potatoes are cooked, sprinkle over the chives and dried cranberries and serve straightaway with the sauce on the side or drizzled over the top.