Heat oven to 425°. Cut butter and 3-ounce package of cream cheese into Bisquick mix in medium bowl, using pastry blender or crisscrossing 2 knives, until mixture looks like fine crumbs. Stir in milk and egg yolk. Place dough on surface well dusted with Bisquick mix; gently roll in Bisquick mix to coat. Shape into a ball; knead 10 times.