For the frosting: 1 1/2 cups confectioners' sugar 3 tablespoons reduced-fat Neufchâtel 3 tablespoons light butter from a stick, softened 1/2 tablespoon fat-free milk 1 teaspoon vanilla extract
For the buns: Butter-flavored cooking spray 2 tablespoons light butter from a stick 1 cup fat-free milk 1/3 cup granulated sugar 1/4 cup artificially sweetened fat-free vanilla yogurt 1 egg 1 egg white One 1/4-ounce packet active dry yeast 4 cups unbleached flour, plus more as needed 1 teaspoon plus 1 tablespoon ground cinnamon 1/2 teaspoon salt 3 tablespoons corn syrup 3 tablespoons packed brown sugar 1/2 teaspoon vanilla extract
For the frosting: In a mixing bowl, combine the sugar, Neufchâtel, butter, milk, and vanilla extract. Mix on low speed with an electric mixer fitted with beaters or stir with a spoon until combined, about 1 minute. If using a mixer, increase the speed to high.
Beat or stir vigorously until smooth, about 30 seconds. Allow the frosting to set for at least 10 minutes. Place in an airtight plastic container. Refrigerate for up to 3 days. Just before using, stir well with a spoon.
For the buns: Lightly mist a large bowl with cooking spray. Set aside 1 tablespoon of the butter to soften.
In a large microwavable measuring cup or a medium-sized microwavable bowl, combine the milk, granulated sugar, and the remaining butter. Microwave on high power until the milk is hot (130 degrees), 2 minutes.
Add the yogurt. Whisk until the sugar dissolves (some small lumps of yogurt may be visible). Add the egg and egg white. Whisk to beat well. Add the yeast. Whisk until dissolved.
In the bowl of an electric stand mixer fitted with the dough hook or in a large mixing bowl, combine 2 cups of the flour, 1 teaspoon of the cinnamon, and the salt.
Mix or stir by hand with a wooden spoon to blend. Add the milk mixture. Mix on medium power or stir vigorously to blend. (The mixture will be very sticky.) Add the remaining flour, mixing or stirring until absorbed.
Lightly flour a work surface. Turn the dough onto the work surface. (A plastic dough scraper or brittle plastic spatula is helpful for getting out all of the dough and starting the kneading.)
Knead until smooth and elastic, about 5 minutes. Add scant amounts of flour as needed. (The dough should be soft but not sticky.) Place in the reserved bowl. Lightly mist with cooking spray. Cover the bowl tightly with plastic wrap. Allow to rise until doubled in size, about 1 hour.
Meanwhile, in a small bowl, combine the corn syrup, brown sugar, the remaining cinnamon, and the vanilla extract. Stir to blend well. Set aside.
When the dough has doubled in size, gently punch it down and place it on the lightly floured surface. Knead for about 1 minute. Dust lightly with flour. Cover and let rest for 10 minutes.
Lightly mist an 11-by-7-inch nonstick baking dish with cooking spray. Set aside. Using your hands or a floured rolling pin, press or roll the dough into an 18-by-12-inch rectangle.
With a butter knife, evenly spread the softened butter over the dough. Drizzle on the filling. With a knife or spatula, spread it evenly to the edges. Starting at one shorter side, roll the dough, jelly-roll fashion, into a tube, ending seam side down. Cut into 8 equal pieces. Place, spiral side up, in the reserved dish.
Cover the dish with a damp kitchen towel and place in a warm spot. Let the rolls rise for another 30 minutes.
Preheat the oven to 350 degrees.
Bake until very lightly browned but slightly doughy in the center, 22-28 minutes. With a spatula, transfer 1 roll to a plate. Using a butter knife, spread 1 1/2 tablespoons of frosting over the top and 1/2 tablespoon down the sides. Repeat with the other 7 rolls.