There’s nothing more frustrating than expecting golden, crispy roast potatoes and ending up with limp, soggy chunks instead. But one simple change during the boiling stage could completely transform your next batch. If you’re tired of underwhelming spuds, keep reading—this trick is deceptively easy, yet surprisingly powerful.
The boiling secret that changes everything
The key to ultra-crispy roast potatoes isn’t just high oven heat or a generous pour of oil—it’s what you do before they hit the tray. There’s a time-tested kitchen hack that many home cooks still miss. Ready? It’s all about adding a bit of bicarbonate of soda (also known as baking soda) to the boiling water.
Sounds simple, right? Here’s why it works:
- Bicarbonate of soda raises the pH level of the water, which helps break down the starches on the surface of the potatoes.
- This process creates a rough, fuzzy exterior—perfect for trapping oil and maximizing crispness during roasting.
- The result? More golden edges, deeper crunch, and that satisfying crackle when you take a bite.
The method: how to pull off perfect crispy roasties
Ready to upgrade your potatoes? Here’s how to make them work every Sunday—or anytime you’re hungry for that perfect bite.
Ingredients you’ll need
- 6 medium russet potatoes – peeled and chopped
- 1 tablespoon bicarbonate of soda (baking soda)
- 3 tablespoons olive oil
- 3 garlic cloves – grated
- 1 tablespoon butter
- 1 tablespoon onion granules
- 3 tablespoons fresh or dried thyme
- Salt and pepper to taste
Step-by-step method
1. Prep the boil: Fill a large pot with cold water and stir in 1 tablespoon of bicarbonate of soda. Also, add salt—about 1 tablespoon per litre of water.
2. Parboil the potatoes: Bring the water to a rolling boil. Add your chopped potatoes and parboil them for 10 minutes. This gives them time to soften just enough without falling apart.
3. Preheat the oven: While the potatoes boil, heat your oven to 220°C (about 428°F). Line two trays with parchment paper. Two trays help space out the potatoes and prevent overcrowding, which is key for crisping.
4. Drain and season: Once boiled, drain the potatoes and place them in a large mixing bowl. Add the olive oil, garlic, onion granules, butter, salt, and pepper. Gently toss until everything is well coated—you want every edge glistening.
5. Arrange for roasting: Place the potatoes on the baking trays, cut-side down. Spread them out so none overlap—airflow is your friend here.
6. First roast: Bake for 30 minutes without touching them. Let them build that vital crust.
7. Flip and finish: After 30 minutes, turn the potatoes and sprinkle over the thyme. Roast for another 20 minutes. When time’s up, you’ll pull out something truly special—golden, crunchy potatoes with soft, fluffy centers.
Why this works better than traditional methods
Most people skip straight from boiling to baking without thinking much about chemistry. But by tweaking the water’s pH level, you’re using science to your advantage. Think of it this way:
- Baking soda = crispier texture
- More surface starches = better caramelization
- Less guessing = more consistent crunch every time
It’s an old-school trick that feels brand new once you taste the result.
Bonus tips to make them even better
- Use russet or Maris Piper potatoes for the best texture—they’re high in starch and perfect for roasting.
- Don’t skip the garlic and onion granules. They add rich depth of flavor and complement the crispiness beautifully.
- Let leftovers cool on a rack if you’re saving extras—this helps them retain their crunch.
The final bite
Who knew one spoonful of bicarbonate of soda could make such a dramatic difference? This small change turns roasted potatoes from decent to downright addictive. Whether you’re prepping for Sunday lunch or a holiday feast, this crackling, golden side dish deserves a place at your table.
So next time you’re peeling potatoes, remember—the roast begins in the boil.
