Homemade gochujang

Step 1: Clean the fermenting jar (3 litres, glass or onggi): wash it in hot soapy water, rinse, then dry a glass jar in a 250°F oven for 10 minutes, or scald an onggi with boiling water and dry it in the sun. Every bowl, spoon and lid must be bone dry.

Step 2: Whisk 2 ½ oz barley malt powder (yeotgireum) into 5 cups water in a large bowl and leave it for 1 hour, squeezing the powder between your fingers every 15 minutes to release the enzymes. Strain through a fine cloth, squeezing hard, and discard the husks; you should have about 1 litre of cloudy, beige liquid.

Step 3: Warm the malt water in a heavy pot to 55–140°F (use a thermometer; it should feel very hot but not scalding). Whisk in 10 ½ oz glutinous rice flour (chapssal-garu) until no lumps remain.

Step 4: Hold the mixture at 55–140°F for 2 hours, on a rice cooker's keep-warm setting or the lowest heat with the lid ajar, stirring every 20 minutes. It is ready when the thick batter has turned into a sweet, runny liquid that pours like thin cream.

Step 5: Bring it to the boil, then simmer over a medium-low heat for 40–50 minutes, stirring often and scraping the bottom, until reduced by about a third, pale tan and bubbling in thick, lazy blips. Stir in 9 oz rice syrup (ssal-jocheong).

Step 6: Take the pot off the heat and cool to lukewarm (about 104°F), stirring now and then so a skin does not form; this takes 1–2 hours.

Step 7: Beat in 2 ⅛ oz fermented soybean powder for gochujang (meju-garu) until smooth, then add 9 oz fine Korean chilli powder (gochujang gochugaru) in three batches, beating with a wooden spoon after each, and finally 4 oz coarse sea salt. Keep beating until the paste is glossy, evenly red and thick enough to hold a ridge. It should taste very salty, sweet and hot.

Step 8: Spoon the paste into the jar, filling it no more than two-thirds full because it rises as it ferments. Smooth the top, scatter 1 tbsp coarse sea salt, for the surface over the surface, cover the mouth with a clean cloth tied on with string, then put the lid on loosely.

Step 9: Leave it to ferment in a sunny, airy place (a balcony is ideal) for 1–3 months; at least 4 weeks before eating. On dry, sunny days take the lid off and leave the cloth on; close it at night and in rain. Normal signs: the colour deepens, small bubbles form, the paste rises a little and smells sweet and earthy. A thin flat white film can be scraped off with the salt layer. Fuzzy green, black or pink mould, a slimy surface or a rotten smell mean it has spoiled: throw it away.

Step 10: When it tastes rounded and savoury, spoon it into smaller clean jars with a dry spoon and keep it in the fridge for up to a year. Always use a clean, dry spoon, and discard it if mould, sliminess or an off smell ever appears.