Preheat the oven to 200C/180C Fan/Gas Mark Thinly slice the baby potatoes 0.5cm apart, 3/4 of the way through across the width. Place wooden skewers either side to help avoid slicing all the way through. Roast in an oven tray for 25-30 minutes along side the garlic bulb and a drizzle of olive oil.
For the fondue, bring the white wine to a boil and simmer until reduced by half. Add the milk to the pan along with the mustard powder and paprika and gently warm until just simmering. Stir through the cheese to melt and add the cornflour and water slurry and simmer until thickened.
In a suitable casserole dish pour the fondue in to the bottom and top with the roasted hasselback potatoes. Scatter over the sage leaves and season with the coarse black pepper and a pinch of sea salt. Return to the oven and bake for 20 mins until the fondue is bubbling and the potatoes are crisp. Great as a luxurious side dish to your dinner table or as a meal on its own.