Heat milk in saucepan until steaming. Add butter, stirring to melt. Stir in sugars and salt. Remove from heat; let cool to lukewarm.
Sprinkle yeast over warm water in medium-size bowl; let stand until foamy, about 5 minutes. Stir to dissolve yeast. Let cool to lukewarm.
Stir eggs, sour cream and milk mixture into yeast mixture. Stir in 2 cups flour until well blended and smooth. Stir in 2 more cups flour; knead until dough comes together.
Transfer to lightly floured board; knead until smooth and elastic, adding as much of the 1/3 cup flour as needed to prevent sticking. Place dough in buttered bowl, turning to coat. Cover; let rise in warm place until double in bulk, about 1-1/2 hours.
Mix butter, sugar, pecans and cinnamon in small bowl. Set aside.
Melt butter in dish in microwave oven or in small saucepan over low heat. Pour 3 tablespoons into 13 x 9 x 2-inch baking pan. Add brown sugar and maple syrup to melted butter; stir to dissolve sugar. Arrange pecans on top. Grease sides of pan with butter.
Punch dough down; shape into ball. Roll out on lightly floured surface to 24 x 10-inch rectangle. Brush dough with remaining 1 tablespoon melted butter. Sprinkle filling evenly over dough. Starting from long side, roll up dough, jelly-roll style. Cut dough crosswise into 15 equal slices, about 1-1/2 inches each. Arrange pieces, cut side down, in baking pan.
Coat sheet of waxed paper with nonstick cooking spray; place, coated side down, over buns. Let rise in warm place, until doubled in bulk, about 45 minutes.
To bake, heat oven to 350 degrees F. Bake buns 25 to 28 minutes, until they are golden brown and sound hollow when tapped with fingertip. If buns start to brown too quickly, cover with foil.
. Run knife around edges of pan to loosen. Place jelly-roll pan over top of pan; invert baking pan along with jelly-roll pan; shake gently. Remove baking pan, letting topping drip over buns; scrape off any topping that sticks to bottom of pan. Serve immediately. Makes 15 buns.