In a large bowl, dissolve yeast in warm water. Add the buttermilk, sugar, butter, salt and 1-1/2 cups flour. Beat just until moistened. Add egg; beat for 2 minutes. Stir in enough remaining flour to form a soft dough. Turn onto a lightly floured surface; knead until smooth and elastic, about 6-8 minutes.
Place in a bowl coated with cooking spray, turning once to coat top. Cover and let rise in a warm place until doubled, about 1 hour.
For filling, combine the first seven filling ingredients. Punch dough down. Turn onto a lightly floured surface. Roll into a 16x9-in. rectangle. Spread butter over dough. Sprinkle pear mixture to within 1/2 in. of edges. Sprinkle with sugar.
Roll up jelly-roll style, starting with long side; pinch seams to seal. Place seam side down on a baking sheet coated with cooking spray. Pinch ends together to form a ring.
With scissors, cut from outside edge to two-thirds of the way toward center of ring at 1-in. intervals. Separate strips slightly; twist to allow filling to show. Cover and let rise in a warm place until doubled, about 50 minutes. Brush dough with egg.
Bake at 375° for 20-25 minutes or until golden brown. Cool on a wire rack.
For glaze, combine confectioners' sugar, vanilla and enough milk to achieve drizzling consistency. Drizzle over ring.