Dissolve yeast following package direction. Place all the flour, sugar, salt in mixing bowl. Heat the milk and butter to 100-110F in the microwave or pan. Add dissolved yeast, milk and butter mix to flour. With dough hook attached, start mixing on low speed until all ingredients are combined. Turn up speed and beat for about 2 min. until a smooth, springy dough ball is formed. Place dough in lightly floured mixing bowl, cover with a clean kitchen towel and let rise until doubled in size in a warm, dry place, about 1 hr. Preheat oven to 400F. When dough has risen, knead through, cut in half and roll out to fit 2 11X9 inch baking pans. Sprinkle lightly with breadcrumbs, this will soak up excess juices from the plums. Place rows of plums standing on edge, gently pushing into the dough. Let rise for 10 more minutes on top of oven, sprinkle with cinnamon sugar. Bake for 35-45 minutes Let cool and serve with whipped cream or your favorite vanilla ice cream. *Apples are a delicious substitute when plums are out of season. Peeled, cored and sliced, placed on edge in rows.