Nigella Lawson has shared a simple yet effective kitchen tip that could change the way people cook potatoes.

The celebrity chef says the water used to boil potatoes should never be poured down the drain. Instead, she recommends keeping it to make "the best vegetable soup in the world."

The advice appears in her cookbook At My Table: A Celebration of Home Cooking, where she shares practical tips alongside her signature recipes.

The tip also reappears in her Garlic and Parmesan Mash where she explains that the starchy water left behind after boiling potatoes is a valuable ingredient.

Rather than wasting it, she suggests using it as a base for a quick pea soup by cooking frozen petits pois in the liquid before blending until smooth.

The result, she claims, is so delicious that throwing the water away would be a mistake.

She also says that it can be stored in the fridge for up to five days, making it easy to use later.

Nigella also incorporates the water back into her mashed potatoes, insisting that at least 250ml should be added for a smooth, creamy texture.

While some may prefer a firmer mash, she argues that the potato water helps achieve the best consistency.

She also suggests boiling garlic cloves with the potatoes, which gives the mash a subtle sweetness without overpowering the dish.

Beyond soup and mash, the starchy water has other uses. Some home cooks use it to thicken sauces, add depth to bread dough, or even as a natural plant fertiliser due to its nutrients.

Nigella also shares a clever way to use up leftover mash - pressing it into a waffle maker to create crispy potato waffles, which she says make a great alternative to hash browns.

The full recipe for Nigela’s Garlic and Parmesan Mash:

Ingredients:

• 2kg potatoes, such as Maris Piper, peeled and cut into large equal-sized chunks
• 8 fat garlic cloves, bruised and slightly splintered with the flat side of a wide-bladed knife, then slipped out of their skins
• 2 tsp sea salt flakes, plus extra to taste
• 75g unsalted butter, softened
• 50g Parmesan, finely grated

For the optional topping:

• 50g dried breadcrumbs or panko
• 50g unsalted butter, in blobs or teaspoons
• 35g Parmesan, finely grated