In a small bowl, dissolve yeast and 1 teaspoon sugar in warm water. In a large bowl, combine the milk, butter, egg yolks, salt, yeast mixture, remaining sugar and 1 cup flour; beat on medium speed for 3 minutes. Stir in enough remaining flour to form a soft dough (dough will be sticky).
Turn onto a floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl, turning once to coat the top. Cover with plastic wrap and let rise in a warm place until doubled, about 1 hour. Punch dough down.
Turn onto a lightly floured surface; divide dough in half. Press each portion into a greased 13-in. x 9-in. baking pan. Spoon apricot filling over one pastry and cherry filling over the other.
In a large bowl, combine flour and sugar; cut in butter until mixture resembles coarse crumbs. Sprinkle over tops. Cover and let rise until doubled, about 45 minutes.
Bake, uncovered, at 375° for 35-40 minutes or until golden brown. Serve warm. Yield: 2 coffee cakes (15 servings each).