Rosamunda is a waxy-floury all-rounder with a faint sweetness, and it makes exceptional fries if you treat it in two stages. A vinegar blanch sets the outside so the inside steams fluffy, a chill firms the surface, and two passes in coconut oil give you a thin blond crust that shatters rather than bends. Coconut oil works here because it is stable at frying heat and adds only a whisper of flavour.
Cut the potatoes into 1 cm thick batons, keeping them as even as you can — uneven batons fry unevenly and you will end up with pale centres and burnt tips. Drop them straight into a bowl of cold water as you go so they do not discolour.
15 min · until all 1,2 kg cut into even 1 cm batons
Using: Chef's knife, Cutting board, Mixing bowl
Bring 2 l water to a rolling boil in a stockpot with 2 tbsp white wine vinegar and 2 tbsp fine salt. Add the potatoes and blanch them until the edges are translucent and a baton bends without snapping, then drain into a colander and spread on a tray to stop the cooking.
7 min · until the edges translucent and a baton bends without snapping
Using: Stockpot, Colander
Spread the blanched batons in a single layer on a sheet pan without crowding, and refrigerate them uncovered for at least 1 hour — overnight is better. The cold surface dries and firms, and that dry skin is what crisps in the oil.
1 hr · until the surfaces dry to the touch and slightly tacky, not wet
Using: Sheet pan
Pour 1200 g coconut oil into a deep-fry pot, no more than half full, and heat it to 140 °C. Check with an instant-read thermometer and hold it there — coconut oil overshoots fast, so drop the heat the moment it goes past.
8 min · until the oil reads 140 °C and a potato baton dropped in releases a slow, lazy stream of bubbles
Using: Deep-frying pot, Instant-read thermometer
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Fry the potatoes in batches so the oil never drops below 130 °C, until they are pale, floppy and cooked through but not coloured. Lift each batch out with a spider strainer and spread on a tray.
5 min · until pale and floppy with no colour at all
Using: Deep-frying pot, Spider strainer, Instant-read thermometer, Sheet pan
Let the par-fried potatoes cool at room temperature for at least 30 minutes, or refrigerate them for up to 24 hours. Pulling the heat out of the middle is what stops the second fry from burning the outside before the inside finishes.
30 min · until cool to room temperature throughout
Using: Sheet pan
Raise the coconut oil to 190 °C. Fry the cooled potatoes in batches until they float and are deep gold with audible crackling at the edges, then lift out and drain on a rack or paper.
3 min · until deep gold, floating, and crackling at the edges
Using: Deep-frying pot, Spider strainer, Instant-read thermometer, Tongs
Tip the hot fries into a bowl, scatter flaky sea salt and freshly ground black pepper over them while the oil is still glistening, and toss once. Salt now, not at the table — it sticks to hot oil and to nothing at all once they cool.
Using: Mixing bowl, Tongs