Step #1 To prepare bread, dissolve yeast & 1 tbsp granulated sugar in warm milk In a large-ish bowl; let this stand 5 mins.
Step #2 Stir in 1/4 c butter, vanilla, & egg yolks.
Step #3 Lightly spoon flour into dry measuring c, & level with a knife.
Step #4 Add 4 1/2 c flour, 3 tbsps granulated sugar, & salt to yeast mixture; stir this to form a soft dough.
Step #5 Turn dough out onto a floured surface.
Step #6 Knead until smooth & elastic (about 10 mins); add enough of remaining flour, 1 tbsp at a time, to prevent dough from sticking to hands (dough will feel tacky).
Step #7 Place dough In a large-ish bowl coated with cooking spray, turning to coat top.
Step #8 Cover up & let rise in a warm place (85°), free from drafts, 1 hr or until doubled in size.
Step #9 Punch dough down, & let rest 5 mins.
Step #10 Divide in half.
Step #11 Working with one portion at a time (cover the remaining dough to keep from drying), roll each portion into a 14 x 7-inch rectangle on a floured surface.
Step #12 Combine the brown sugar & cinnamon.
Step #13 Sprinkle top each dough portion with half of brown sugar mixture, leaving a 1/2-inch border.
Step #14 Roll up each dough rectangle tightly, starting with a short edge, pressing firmly to eliminate air pockets, & pinch seams & ends to seal.
Step #15 Cut each dough roll crosswise into 3 pieces.
Step #16 Place 3 pieces, cut sides up, into each of 2 (8 x 4-inch) loaf pans coated with cooking spray.
Step #17 Cover up & let rise 30 mins or until doubled in size.
Step #18 Preheat oven to 350°.
Step #19 Uncover dough, & bake this at 350° for 35 mins or until loaves are browned on bottoms & sound hollow when tapped.
Step #20 Cool in pans 10 mins on a wire rack, & remove this from pans.
Step #21 Brush tops of loaves with melted preserves.
Step #22 Cool loaves on rack.
Step #23 To prepare the glaze, beat 1 tbsp butter at lowish speed of a mixer until creamy.
Step #24 Add remaining ingredients, beating just until mixed.