Step 1

Preheat oven to 220°C/450°F top bottom heat, or 200°C/400°F convection. Peel potatoes and cut them into big chunks, about 4 - 5 cm (1 - 2 in.) in size. Bring 2L water to a boil in a large pot over high heat. Add salt, baking soda, and potatoes. Stir to combine. Bring to a boil again, reduce heat to a simmer and cook for approx. 10 min., or until a knife meets little resistance when piercing a piece of potato.

Step 2

In the meantime, finely chop the garlic. Pluck rosemary leaves and chop finely. In a small saucepan, combine olive oil with chopped rosemary, garlic, and some black pepper, and heat over medium heat. Stir constantly until the garlic just begins to turn slightly golden, about 3 min.. Immediately drain the oil through a fine strainer in a large bowl. Set the garlic-rosemary mixture aside in a small bowl.

Step 3

When potatoes are cooked, carefully drain them and put them back in the pot for about 30 seconds, to allow excess moisture to evaporate. Add potato pieces to the bowl with the oil, season with a little more salt and pepper, and toss until a thin layer of the mushy surface has formed.

Step 4

Put the potatoes on a baking sheet lined with parchment paper and spread them out evenly. Place in the oven and roast for approx. 20 min. Then use a metal spatula to loosen the potatoes and turn them over. Continue roasting until potatoes are deep brown and crispy all over, turning several times, for another approx. 40 min. Meanwhile, rinse the lemon under hot water and grate some of the zest and add to the garlic-rosemary mixture. Remove the potatoes from the oven, toss with the garlic-rosemary mixture, and season with more salt and pepper. Serve immediately.