Preheat the oven to 200C fan/gas mark 7. Pour 6 tablespoons of oil into a very large roasting tray with the garlic bulb halves and a generous sprinkle of salt. Place the roasting tray in the oven to heat.

Put the potatoes into a large pan and cover with cold water. Add 1 tablespoon of salt and bring to the boil, then reduce the heat and simmer for 5 minutes. Drain the potatoes, then return them to the pan to steam for 2 minutes. As the potatoes are steaming, shake the pan to rough up their edges for maximum crispiness.

Remove the hot roasting tray from the oven and carefully add the potatoes in a single layer, being careful not to overcrowd the tray. Toss the potatoes in the hot oil until they are fully coated, then season generously with salt and pepper. Roast for 45 minutes or until golden and crispy, turning the potatoes over halfway to ensure even roasting.

In the last 10 minutes of the cooking time, prepare the stir-fried spring onions and the soy dressing. Heat 2 tablespoons of oil in a frying pan over a medium heat and add the spring onions, garlic, and ginger. Cook for 2–3 minutes until fragrant and just beginning to soften, then remove from the heat. To make the dressing, mix the vinegar and soy sauce in a small bowl and set aside.

Once golden, toss the potatoes with the spring onion, garlic, and ginger, then drizzle over the vinegar and soy dressing. Serve immediately.