In a small bowl combine the yeast, water, and 2 Tbsp of sugar. Let stand 10 minutes for yeast to proof. Meanwhile in a large bowl combine the remaining sugar, butter, milk, egg yolks, flour, and salt. Add the yeast mixture and mix until a stiff dough forms.
Turn the dough onto a floured surface and knead until smooth and elastic, about 7-8 minutes. Grease a large bowl and add dough, covering with plastic wrap and set in a warm place to rise until doubled, about an hour.
Punch dough down and cover, rising for an additional 30 minutes. Take dough from bowl and roll out on a floured surface to 1/2-inch thickness. Cut with a round cookie cutter or a large drinking glass. Spray baking sheets with cooking spray and place dough rounds on sheets. Let rise once again, about 45 minutes or until doubled. Meanwhile preheat your oven to 350ºF.