Cream Cheese-Filled King Cake

This is from Southern Living. I just made it for the first time and YUM! I used lighter ingredients so that's what I am indicating here--feel free to use the full fat stuff as you wish:)

• Ready In: 1 hr 45 mins
• Serves: 36
• Yields: 2 cakes

Ingredients

• 1 (16 ounce) container reduced-fat sour cream
• 1⁄3 cup sugar
• 1⁄4 cup  Smart Balance butter spread
• 1  teaspoon salt
• 2  tablespoons dry active yeast (or 2 packets)
• 1⁄2 cup warm water (100 to 110 degrees)
• 1  tablespoon sugar
• 2  large eggs, lightly beaten
• 6 -6 1⁄2 cups bread flour (mine took only 5 1/2)
• 3⁄4 cup sugar
• 1 (8 ounce) package  neufchatel cheese, softened
• 1 (8 ounce) package fat free cream cheese
• 1  large egg
• 2  teaspoons vanilla extract
• 3  tablespoons  Smart Balance butter spread
• 3  cups confectioners' sugar
• 1⁄4 teaspoon vanilla extract
• 2  tablespoons milk
•  purple- green-, and gold-tinted sparkling sugar  candy sprinkles

Directions

1. Cook first 4 ingredients in a medium saucepan over low heat, stirring often, until butter melts. Set aside, and cool mixture to 100° to 110°.
2. Stir together yeast, 1/2 cup warm water, and 1 tablespoon sugar in a 1-cup glass measuring cup; let stand 5 minutes.
3. Beat sour cream mixture, yeast mixture, eggs, and 2 cups flour at medium speed with a heavy-duty electric stand mixer until smooth. Reduce speed to low, and gradually add enough remaining flour (4 to 4 1/2 cups) until a soft dough forms.
4. Turn dough out onto a lightly floured surface; knead until smooth and elastic (about 10 minutes). Place in a well-greased bowl, turning to grease top.
5. Cover and let rise in a warm place (85°), free from drafts, 1 hour or until dough is doubled in bulk.
6. Punch down dough, and divide in half. Roll each portion into a 22- x 12-inch rectangle. Beat 3/4 cup sugar, cream cheese, 1 egg, and vanilla at medium speed with an electric mixer until smooth. Spread cream cheese mixture evenly on each dough rectangle, leaving 1-inch borders.
7. Roll up each dough rectangle, jelly-roll fashion, starting at 1 long side. Place one dough roll, seam side down, on a lightly greased baking sheet. Bring ends of roll together to form an oval ring, moistening and pinching edges together to seal. Repeat with second dough roll.
8. Cover and let rise in a warm place (85°), free from drafts, 20 to 30 minutes or until doubled in bulk.
9. Bake at 375° for 14 to 16 minutes or until golden. Slightly cool cakes on pans on wire racks (about 10 minutes).
10. For Glaze: Stir together Smart Balance through vanilla. Stir in 2 tablespoons milk, adding additional milk, 1 teaspoon at a time, until spreading consistency.
11. Sprinkle decorating sugar on top of glaze in bands, if desired.