Roast potatoes require this specific baking soda boiling step first.

Think a glug of searingly hot oil and a blasting oven are all you need for the ultimate Sunday roastie? Think again. Generations of home cooks have relied on the standard parboil-and-shake method, but food science reveals we’ve been missing a crucial ingredient that guarantees an earth-shattering crunch every single time.

The secret isn’t duck fat or semolina—it’s half a teaspoon of baking soda (bicarbonate of soda) added to your boiling water.

The Science of the Perfect Crunch

• Avocados stay entirely green for days using this unexpected submersion technique.
• Feta cheese bakes turn into rubber following this viral recipe.
• Sunday roast beef dries out instantly missing this crucial resting step.
• Tesco olive oil shoppers face sudden rationing amid European droughts.
• Fresh parsley ruins dinner party dishes with this presentation mistake.

Why does this pantry staple make such a difference? It all comes down to alkaline water. When you add baking soda to the pot before parboiling your spuds (Maris Pipers or King Edwards work best), the water’s pH level rises. This alkaline environment breaks down the exterior of the potato far more rapidly than tap water alone.

As the edges soften and break apart, they create a starchy, mashed potato-like slurry on the surface of each chunk. When you drain and ‘chuff’ (shake) the potatoes in the colander, this starchy paste coats the spuds completely. Once they hit the hot fat in your roasting tin, that slurry dehydrates and fries, forming an incredibly thick, glass-like crust while the inside remains wildly fluffy.

How to Do It

Here is your new foolproof method for the ultimate weekend roast:

• Peel and cut your potatoes into large, even chunks.
• Bring a large pot of water to a rolling boil and stir in half a teaspoon of baking soda along with a generous pinch of salt.
• Boil the potatoes for 20 to 25 minutes until tender. Don’t worry if the edges look a bit fuzzy—that’s exactly what you want!
• Drain well, return to the hot pot, and give them a vigorous shake to build up that starchy coating.
• Transfer to a pre-heated roasting tin filled with smoking hot oil (or goose fat) and roast at 220C for 45 to 50 minutes, turning halfway.

Next time you’re prepping Sunday lunch, skip the flour dusting. A simple pinch of baking soda is the only trick you need for the crispiest, crunchiest roast potatoes of your life.