Combine the sourdough discard, water and flour into the bowl of your stand mixer or Thermomix 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.
Now you need to let your dough rise. You are using instant yeast as the leavening agent in this recipe, rather than sourdough/wild yeast, so it will rise very quickly, particularly if your home is warm. 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.
Once the dough has risen, you'll need to bake your loaf. Turn your oven on and set the temperature to around 180C/350F. Let it warm for around 10 minutes. Spray the top of your dough with some water mist and place into the oven. Make sure that there's plenty of room for it to grow in the oven as it will generally keep rising.
Bake your bread at 180C/350F for around 40 to 45 minutes or until the loaf is golden brown.
Remove from the loaf tin and allow to cool on a wire rack.
This recipe is a "sourdough discard" recipe - so it's based on using unfed sourdough starter that you accumulate when you're building a sourdough starter or when you feed it ready to bake.I choose to use a stand mixer or Thermomix for this recipe as it allow me to achieve a super stretchy, silky dough that gives my sandwich bread a soft, airy texture - perfect for sandwich bread!