Instructions
Start with the sponge: Place the milk, yeast, egg, and 1 cup of flour in the bowl of a stand mixer. Mix the ingredients with a spatula until combined (it will be very sticky).
Sprinkle the remaining cup of flour on top, covering the sponge completely, and let it rest in a warm place for 30 minutes (no need to cover the bowl with plastic wrap).
After 30 minutes, check that there are cracks in the flour (see blog photo). The cracks let you know that the yeast are alive and well.
Continue with the dough: Add the sugar, salt, eggs, and 1 cup of the flour to the sponge. Fit the bowl on your stand mixer, and using the dough hook, mix on low for 1 minute, until the dough starts to come together. With the mixer still running on low, add the remaining 1/2 cup of flour.
When the flour has been incorporated, increase the speed to medium, and mix for 15 minutes. After 10 minutes have passed, if the dough seems too loose, add 3 additional tablespoons of flour, to help the dough form into a cohesive piece. Make sure you don’t skimp on kneading the dough for 15 minutes.
Turn the mixer down to medium low speed and add the butter, a couple pats at a time, waiting until each installment of butter is absorbed before adding the next. When all the butter has been added, bump the speed up to medium high for a minute, then reduce to medium and knead the dough for 5 minutes. The dough will be soft and slightly sticky.