Stand Mixer Method: Fit your stand mixer with the dough hook attachment. In the mixer bowl, whisk together the sweet starter, warm milk, honey, sugar, salt, and egg until well combined. Add 450g of bread flour and mix on low speed until a rough dough forms.
With the mixer running on low, gradually add the softened butter, one small pat at a time, allowing it to fully incorporate before adding more. This step should take about 5-8 minutes. The dough will be soft and slightly sticky—this is normal for a high-hydration dough.
Hand Mixing Method: In a large bowl, whisk together the sweet starter, warm milk, honey, sugar, salt, and egg until smooth. Add 450g of bread flour and mix with a wooden spoon or dough whisk until a shaggy dough forms.
Add the softened butter in small pieces, kneading it in by hand. Perform three sets of stretch and folds over the next 90 minutes, resting the dough for 30 minutes between each set. The dough will gradually strengthen and become smoother.