385gbread flourThe same weight of all-purpose flour also works.
360mlkefir wheyPlain, unsalted kefir whey, bought or strained from plain milk kefir.
1½tspactive dry yeastDissolve in the warm whey before adding to the flour.
1tspsalt
1tspsugar
1tbspolive oil
1tbspunsalted butterSoften before greasing the pan.
You will need
Kitchen scale and measuring spoons
Measuring jug
Small saucepan
Large mixing bowl and spatula
Clean damp kitchen towel
Loaf tin, about 23 × 13 cm
Oven
Cooling rack
Food thermometer
Instructions
Gently heat the whey to about 38°C (100°F); it should feel lukewarm, not hot.
Stir the sugar and yeast into the warm whey and leave for 5–10 minutes, looking for foam on the surface. If no foam appears, start again with fresh yeast.
Mix the flour and salt in the bowl, then stir in the yeast mixture and olive oil to form a wet, sticky dough with no dry flour left. No kneading is needed.
Cover the bowl with the damp cloth and let the dough rise in a warm place for 1–2 hours, until doubled in volume.
Spread the softened butter generously over the base and sides of the loaf pan.
Gently press the dough down with the spatula, then scrape it into the buttered pan and ease it into a rough loaf shape.
Cover the pan and let the dough rise for 45–60 minutes, until its rounded top sits just above the rim.
Near the end of the second rise, preheat the oven to 220°C (425°F).
Uncover the pan and bake for 15 minutes, then reduce the oven temperature to 190°C (375°F) and bake for another 25–30 minutes, until deeply golden and about 93°C (200°F) in the centre.
Remove the loaf from the pan and cool on the rack for at least 20 minutes before slicing.
The dough should be wet and sticky but hold together rather than flow like soup. Use the spatula to handle it; do not add flour just to stop it sticking.
Storage and safety
Cool completely, then keep in a sealed bag at room temperature for up to 2 days. For longer storage, slice the loaf, seal in a freezer bag and freeze for up to 3 months. Reheat slices in a toaster as needed.