In a mixing bowl pour ½ Cup lukewarm milk and dissolve 1 tsp of the sugar in the liquid. Sprinkle the yeast over the milk and mix gently until combined. Allow the mix and yeast mixture to stand for about 10-20 minutes to activate the yeast. The mixture should be bubbly and frothy on the surface.
Once the yeast has become activated you can add in the rest of the sugar, the starter, egg, and flour.
Use a spatula to mix the dough and combine the ingredients, forming a raggedy dough.
Using the dough hook attachment on your mixer, knead the dough for about 5 minutes at a low speed. The dough will be very sticky, but if you keep kneading it will come together.
After 5 minutes of kneading the dough, add in the butter in 3-4 increments. Mix about 20 seconds between each addition. Scrape the sides and the bottom of the bowl to make sure it is mixing well.
Once all of the butter has been added, turn the speed on the mixer up to a medium speed and continue kneading for 5-7 minutes. Scrape the sides and bottom of the bowl once or twice while kneading.
The dough should become smooth, satiny, and pull cleanly from the bowl sides.
Place the dough onto a lightly floured surface and form into a ball. Put the dough in a lightly greased bowl and cover with plastic wrap.
Keep the bowl in a warm place and allow it to double in size. This will take approximately 1-2 hours depending on the temperature of the room.