Grain porridges: semolina, polenta, oats, millet

Why

Semolina, cornmeal and oats are mostly starch, and when they are tipped into hot milk or water all at once, the surface of each clump gelatinises instantly and traps dry flour inside as a lump, just as in thickening (Thickening with starch card); that is why they are poured in a thin stream while whisking constantly. Fine semolina softens in a few minutes, classic polenta from coarse cornmeal needs half an hour to an hour depending on the grind, and porridge cooked too briefly tastes raw and floury. Oats make porridge creamy thanks to beta-glucans, a soluble fibre that thickens the liquid, and every porridge thickens considerably as it cools, because the starch sets again. Milk and starch easily scorch on the bottom, so porridge is cooked in a heavy-bottomed pot over gentle heat and stirred right down to the bottom. Spores of the bacterium Bacillus cereus can survive in cooked grains, and when porridge cools slowly in the warm, they germinate and can form a toxin that later reheating does not destroy.

How to do it

• Bring the liquid almost to the boil and pour in the semolina or cornmeal in a thin stream while whisking constantly.
• Cook over gentle heat in a heavy-bottomed pot and stir right down to the bottom; polenta only needs stirring every few minutes, semolina and oats more often.
• Cook porridge a little thinner than you want to serve it; it will thicken further on the plate.
• Rinse millet with hot water before cooking and taste it; throw out millet that is bitter or rancid when dry, rinsing won't fix it.
• Leftover polenta or semolina porridge can be poured into a tin, left to set, sliced and fried.
• Spread leftover porridge in a shallow container and refrigerate it within 2 hours; rice congee within 1 hour, like cooked rice.

If it goes wrong

Whisk out lumps or blend them with an immersion blender; push large lumps through a sieve. Loosen set porridge with a little hot milk or water and heat it until piping hot throughout, stirring constantly. Pour scorched porridge straight into a clean pot without scraping the bottom; if it already tastes burnt, it can't be saved. Porridge that tastes raw and floury just needs a few more minutes of cooking and a little liquid.