Combine the sourdough discard, water and flour into the bowl of your stand mixer and mix until it forms a shaggy dough (around 30 seconds will do it). Leave the dough to rest for 30 minutes.

Now add the salt, sugar, butter and yeast to the bowl and knead the dough for around 3 to 6 minutes.

You want the dough to be elastic, silky and slapping the sides of the bowl. Just keep the mixer going until you achieve this. If you are using a stand mixer you'll need to use your dough hook attachment for this step. The dough should be completely off the sides of the mixing bowl.

Now you need to let your dough rise. You are using instant yeast as the leavening agent in this recipe, rather than all sourdough, so it will rise very quickly, particularly if your home is warm. Cover your bowl with a moistened tea towel to keep in moisture. Leave it for around an hour (it will take longer if your house is cooler). You want it to double.

While you're waiting for the dough to double, lightly butter a sandwich loaf or pullman pan so it's ready to go when the dough is shaped.

Once the dough has doubled, tip it out onto the counter top with the smooth side underneath and the sticky side on the top. Gently ease the dough out into a rectangle. It should be quite easy to do this as the dough is very elastic.

Now you want to shape your dough into a sandwich loaf. This is fairly easy. Make sure that the short side of the rectangle is in front of you. Fold each side of the dough into the middle, then roll the dough into a tight log with the seam underneath. Tighten the top of the dough by putting your hands at the base and pulling the dough towards you, without lifting if off the countertop.

Once the dough is shaped, gently place it into the buttered loaf tin. Leave the dough to rise until it's just above the rim of the tin.

This will take around an hour, depending on the temperature of your home. Cover with moist tea towel.

Enjoy!