In a small bowl, dissolve yeast and 1 teaspoon sugar in 1/4 cup warm water; let stand for 5 minutes. In a large bowl, combine the butter, eggs, milk powder, salt, yeast mixture, remaining sugar and water and 2-1/2 cups flour. Beat until smooth. Stir in enough remaining flour to form a soft dough.
Turn onto a floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl, turning once to grease top. Cover and let rise in a warm place until doubled, about 1 hour.
Sprinkle pecans into two greased 9-in. round baking pans. Combine the brown sugar, cornstarch, cinnamon, vanilla and salt; sprinkle over pecans. Drizzle with butter.
Divide dough in half; shape each portion into 15 balls. Place over topping. Cover and let rise in a warm place until nearly doubled, about 45 minutes.
Bake at 375° for 30 minutes or until golden brown. Cool for 1 minute; invert onto a serving platter.
Editor's Note: Coffee cakes may be frozen before baking and thawed for 4 hours in the refrigerator. Place in a cold oven; set oven to 375°. Bake for 35-40 minutes or until browned.