Leek & Potato Soup

Even pieces cook evenly. Sweet potato is harder and more slippery than normal potato, so take care.

1. Scrub off any soil under the tap. Peel with a vegetable peeler, working away from you — or leave the skin on for roasting and wedges.
2. Cut a thin slice off one side so the potato sits flat and cannot roll.
3. Cut it into slabs, then the slabs into sticks, then the sticks across into cubes of the size the recipe wants.

A boil is big bubbles rolling hard across the whole surface. A simmer is much gentler: small bubbles rising lazily, a few breaking the surface. Stews, sauces and soups simmer; boiling makes meat tough and sauces catch on the bottom.

1. Bring it up to the boil on a higher heat, then turn the heat down until the bubbling calms to a gentle simmer.
2. Check every few minutes and adjust — a lid on makes it hotter, a lid off lets it thicken.
3. Stir now and then, scraping the bottom, so nothing sticks and burns.

Ready when: Small, steady bubbles — not a still surface, not a rolling boil.

Blenders are simple, but hot liquid expands and can blow the lid off.

1. Never fill more than halfway, and never more than a third with anything hot.
2. Hold the lid down with a folded tea towel and start on the lowest speed, then turn it up.
3. Always switch off at the wall before putting a spoon or finger near the blades.