Combine 1-1/2 cups flour, sugar, undissolved yeast and salt in large mixer bowl. Heat milk, water and 1/3 cup butter until very warm (120° to 130°F); butter does not need to melt. Add to flour mixture; beat 2 minutes at medium speed of electric mixer, scraping bowl occasionally. Add eggs and 1/2 cup flour; beat 2 minutes at high speed, scraping bowl occasionally. Stir in remaining flour to make stiff batter; grease top. Cover tightly with plastic wrap; refrigerate 2 hours or up to 2 days.
Remove dough from refrigerator and punch dough down. Remove dough to lightly floured surface; divide in half. Set aside 1 half. Roll remaining dough to 16x10-inch rectangle. Melt remaining 1/4 cup butter; brush 2 tablespoons over dough. Sprinkle evenly with half of cinnamon filling. Beginning at long end, roll up tightly as for jelly roll; pinch seam to seal. With sharp knife, cut roll into 16 equal pieces. On lower third of large greased baking sheet, arrange 5 rolls, cut sides up, in a row with edges touching. Form tree shape with additional rows of rolls - 4 rolls in second row, 3 rolls in third row, 2 rolls in fourth row, and 1 for top of tree. Place remaining roll at bottom center of tree to make trunk. Repeat with remaining dough, butter and filling. Cover; let rise in warm place until doubled in size, about 30 to 45 minutes.
Bake at 375°F for 15 to 20 minutes or until done, switching positions of sheets halfway through baking time for even browning. Remove from sheets; let cool on wire racks. Drizzle with Vanilla icing. Decorate "trees" with colored icings, sprinkles or candies if desired.
Cinnamon Filling: Combine sugar and cinnamon in a small bowl. Stir well.
Vanilla Icing: Combine powdered sugar, milk and vanilla in a small bowl. Stir until smooth.
Recipe Note: These are easy to make ahead. You have two choices: you can make the dough and chill up to 2 days, then shape, let rise and bake, as described in the recipe, OR you can make the dough, chill for 2 hours, then shape, cover with plastic wrap that is sprayed with nonstick spray and chill for up to 2 days. Remove the rolls from the refrigerator and let sit at room temperature 30 minutes before baking. Pick the option that works best for you, but don't chill longer than 2 days total.