To a bowl of a stand mixer, add the warm water, sourdough starter, sugar and melted butter to the bowl of a stand mixer with a paddle attachment. Mix on low speed with the paddle attachment until smooth.
You can also mix and knead the dough by hand, but you will need to knead the dough slightly longer, 8-10 minutes, to achieve the windowpane test.
200 grams warm water,200 grams active sourdough starter,25 grams sugar,57 grams unsalted butter, melted
To the wet ingredients, add the flour and salt. With the hook attachment, mix again on low speed. Stop to scrape the sides of the bowl to incorporate all the dry ingredients and then continue to mix on low for 1-2 minutes.
405 grams bread flour,9 grams salt
Once all of the ingredients have been incorporated, continue to knead the dough on medium speed for 6-8 minutes.
You’ll know the dough has been kneaded completely when it is smooth and elastic. The dough will completely pull away from the sides of the bowl when it is being kneaded and it will pass the windowpane test.
This means when you stretch a small section of dough into a thin film, the light will be able to pass through without the dough tearing. If this is accomplished, the dough has been properly kneaded.
Remove the dough and place it in a lightly greased bowl and cover with a reusable cover.