Got into baking sourdough bread during lockdown? Mix it up with this tasty pretzel recipe, from former Great British Bake Off finalist James Morton.

Sourdough pretzels recipe

Ingredients:(makes 12 large pretzels)

For the pretzels:400g strong white flour, plus extra for dusting220g tepid water (see method)150g white sourdough starter7g table saltSea salt flakes, for sprinkling

For the bath:1L cold water20g lye (caustic soda), or 50g bicarbonate of soda (baking soda)

Method:1. In a large bowl, weigh your flour. Mix together some warm and cold water in a jug until it feels just warmer than tepid, about 25ºC (77ºF), then weigh out 220g and add this along with your sourdough starter to your flour. This is a very dry dough. Mix using a wooden spoon, a dough hook or your hands until you’ve got one solid lump. Let your dough rest for approximately 30 minutes – this autolyse, without salt, really helps when managing such tenacity. Cover the bowl with a damp tea-towel or a plate to stop the dough drying out.

2. Add your table salt, then knead your dough for 10–15 minutes, or until it is properly shiny and smooth. The best way to do this is in a stand mixer, to be honest, but otherwise regular kneading will work well. Like with bagels, the pretzel is aided by a good lot of kneading. Leave your dough, covered, for three hours or so at room temperature. Your proving time will vary depending on temperature. Don’t worry about any stretching and folding – it doesn’t need it. The dough should be plenty strong enough.

3. Lightly flour a work surface. Use a dough scraper to move your dough out onto it and then use floured hands to gently roll it out into a big doughy sausage. Use your scraper to chop this into 12 equal pieces – you can weigh them if you want to be conscientious.

4. Prepare two trays by coating them with a tea towel or cloth and flouring it, or by lining with non-stick greaseproof baking paper.

5. You should start like you would with a baguette. Sprinkle a little flour onto the surface and place your first piece of dough on top. Fold each piece like an A4 (US) letter going into a windowed envelope: first the side towards you, and then the side away from you. Tighten it further into a very tight sausage, then use the open palms of your hands to roll this dough backwards and forwards. Keep a chunky bit in the middle about 2.5cm thick, but then taper it each side into thin spindles. The total length should be about 40cm, ideally.

6. Shape the dough into an upside-down ‘U’, with the swollen bit in the middle at the curve of the ‘U’. Twist the two ends around each other two or three times, leaving at least a few centimetres of each strand free at the end. Then invert your ‘knot’, and press each free end onto the edge of the main body of your bagel. Place on your cloth- or paper-covered trays and repeat. Leave your pretzels to prove for an hour or so – no more. This gives you time to clear some space in the freezer. Freezing is an optional step that helps the pretzels hold their shape much better in their caustic bath. Ideally, put your trays of pretzels in the freezer for 30 minutes before dunking.

7. Before you start your bath, preheat your oven to 220ºC (430ºF)/200ºC (400ºF) fan/Gas 7. Pretzels are fine just baked on baking trays, as we’re not after a supremely crisp base. About 20 minutes of preheating will be plenty.

8. Prepare your bath. Don rubber gloves (NOT nitrile or latex) and goggles, and fill a bowl (stainless steel, glass or hard plastic) with the cold water. Add your lye and stir gently until it has completely dissolved – always add lye (caustic soda) to water, never add water to caustic soda, otherwise the exothermic reaction as it dissolves will cause dangerous spluttering. If you’re using bicarb (baking soda), weigh it out and stick it on a baking tray, then bake during your 30 minutes of pretzel freezing in your preheating oven. Stir to dissolve this in your water.

9. Using a gloved hand or a stainless-steel slotted spoon, dip each frozen pretzel into your lye. Hold it here for five seconds, and then remove it, letting any excess drip away. If using baked bicarb, leave it in the bath for roughly 20–30 seconds before draining. Place each nearly-dry pretzel on a new baking tray, preferably lined with some non-stick greaseproof baking paper. (You can take your gloves off now.)

10. Use a lame or razor to score the thick part of all your pretzels and then sprinkle with plenty of sea salt. Place your trays in the oven to bake for about 15–20 minutes. They should be a deep and shiny golden brown, almost like they’re dipped in plastic, with a magnificent pale ‘ear’. Cool for at least 10 minutes before eating.

NB: Caustic solution can be poured down the plug hole to dispose of it – it’ll even take care of any blockages in your drain. Just don’t splash. Any drips may discolour your natural stone or wooden work surfaces.

Sourdough From Scratch by James Morton, photography by Andy Sewell, is published by Quadrille, priced £12.