Gavin’s BEST EVER Roast Potatoes!

Gavin’s BEST EVER Roast Potatoes!
This is cooking with Science! The baking soda (bicarb) is the magic ingredient – it makes the water slightly alkaline. This breaks down the outside of the potatoes and makes a starchy slurry – so the oil sticks to them and they go super crispy when roasted!
Infusing the oil is optional but adds to the flavour.
Adding the oil to the potatoes in the pot seems totally backwards at first. It works because they get smothered in oil but end up roasting on a dry pan rather than sitting in oil (healthier too!).
Preheat oven to 230°C (200°C if using fan).
Peel potatoes and cut into large chunks.
Heat water in a large pot over high heat until boiling. Add 2 tablespoons salt and about 25g of baking soda (bicarbonate of soda, not baking powder or you will make a big mess!). Then add potatoes and stir.
Return to a boil, reduce to a simmer and cook until a knife meets little resistance when inserted into a potato chunk (about 10 minutes after returning to a boil).
Optional infused oil – combine olive oil (include some duck fat if you have it) with rosemary, garlic, and a few grinds of black pepper in a small saucepan and heat over medium heat. Cook, stirring and shaking pan constantly, until garlic just begins to turn golden, about 3 minutes. Immediately strain oil through a sieve set in a large bowl. Set garlic/rosemary mixture aside and reserve separately.
When potatoes are cooked, drain carefully and let them rest in the pot for a few minutes to allow excess moisture to evaporate. Add the infused oil (the oil does NOT have to be hot!), season to taste with a little more salt and pepper, and put the lid on the pot. Toss to coat, holding pot with oven gloves and shaking roughly, until a thick layer of mashed potato–like paste has built up on the potato chunks. Make sure the lid doesn’t come off!
Transfer potatoes to a large rimmed baking sheet using tongs or a spoon – you don’t need to take any of the oil as they are covered in it. Spread potatoes out evenly so air can get all around them.
Transfer to oven and roast, without moving, for 20 minutes. Using a thin, flexible metal spatula to release any stuck potatoes, shake pan and turn potatoes. Continue roasting until potatoes are deep brown and crisp all over, turning and shaking them a few times during cooking, 30 to 40 minutes longer (about an hour in total).
Transfer potatoes to a large bowl and add garlic/rosemary mixture. Toss to coat and season with more salt and pepper to taste.