Step 1

To make the starter, combine the buttermilk, sour cream and water in a medium bowl. Add the bread mix and stir until smooth. Cover with a clean tea towel and set aside, stirring every day, for 2-2 1/2 days or until mixture has a nice sour smell (you don't want it to grow mould).

Step 2

To make the sponge, add the bread mix and water to the starter mixture and stir until well combined. Cover with plastic wrap and set aside for a further 24 hours or until mixture rises slightly.

Step 3

To make the dough, combine the bread mix, water, yeast, salt and sponge mixture in a large bowl. Use a wooden spoon to stir until combined, then use your hands to bring the dough together in the bowl. Turn dough onto a lightly floured surface and knead for 10 minutes or until smooth and elastic. Brush a large bowl with oil to lightly grease. Place the dough in the bowl and turn to coat in oil. Cover with a damp tea towel and set aside in a warm, draught-free place to prove for 1 hour or until dough doubles in size.

Step 4

Preheat oven to 200°C. Sprinkle a baking tray with flour. Punch down the centre of the dough with your fist. Turn onto a lightly floured surface and knead for 5 minutes or until dough is smooth and elastic. Divide dough into 2 equal portions. Shape each portion into a 7 x 35cm oval loaf and place on the prepared tray. Cover loaves with a damp tea towel and place in a warm, draught-free place to prove for 30 minutes or until loaves almost double in size. Use a small sharp knife to score the top of the loaves diagonally. Sprinkle the loaves with a little water. Bake in preheated oven for 30-35 minutes or until bread is golden brown and loaves sound hollow when tapped on the bases. Remove from oven and turn onto a wire rack to cool. Cut sourdough into slices and serve.