In a bowl with an electric mixer, add the slightly cooled milk and butter mixture, 1 tsp of sugar and 2 tsp of active dry yeast. Mix well and let yeast become foamy or bubbly at the top (about 5-10 minutes). Add 1 tsp salt, egg yolks and mix with a dough hook attachment. Slowly add about 3 and a half cups of all-purpose flour, leave the remaining 1/2 cup for kneading.