Sour Cream Yeast Dough :
2-1/4 teaspoons (1 envelope) active dry yeast
1/4 cup warm water 100-110 degrees
3 tablespoons unsalted butter, melted and cooled
2/3 cup sour cream
3 tablespoons granulated sugar
1 large egg
1 teaspoon pure vanilla extract
2-1/2 cups all-purpose flour, plus 1 to 2 tablespoons for kneading, if necessary
1/2 teaspoon salt
1/4 teaspoon baking soda
2/3 cup firmly packed brown sugar
2 teaspoons ground cinnamon
4 tablespoons butter, melted
Translucent Vanilla Glaze:
1-1/4 cups powdered sugar
1 tablespoon unsalted butter, melted
1 tablespoon milk
1 teaspoon vanilla
To make the dough: Combine the yeast with the water in the bowl of a stand mixer. Set aside until foamy, about 5 to 10 minutes. Add the butter, sour cream, sugar, egg, and vanilla and stir to combine with a rubber spatula. Fit the mixer with the paddle attachment, twist on the bowl with the yeast mixture, and add 2 cups of the flour, salt, and baking soda. Mix on medium-low until incorporated. Add the remaining 1/2 cup flour and beat until the dough is soft and smooth.
Knead the dough on a floured surface until it is no longer sticky (you may need to add 1 to 2 tablespoons more flour), about 3 minutes. Place it back in the mixing bowl, cover with plastic wrap, and let rise in a warm spot for about an hour, until doubled in size.
Put a rack in the center of the oven and preheat to 350 degrees. Spray and flour a standard 12-cup muffin tin.
To make the topping: In a small bowl, stir together the brown sugar and cinnamon. Place the melted butter in a small dish nearby.
To shape: Punch down the dough, then form it into a long cylinder. Divide it into 12 equal portions, each one weighing 1-3/4 ounces. Divide each of the 12 portions (I use a bench scraper) into sixths, and roll each little piece into a ball. Roll the balls first in the butter, then in the cinnamon-sugar. Place in the muffin cups. Repeat, placing all 6 balls in the same muffin cup, roughly 5 on the perimeter and 1 in the center, but I found that being particular with the placement wasn't really necessary.
Repeat with the remaining 11 dough portions. When you're done, each muffin cup will be filled with 6 little cinnamon/sugar/butter coated balls, or "bubbles."
Cover the muffin tin with plastic and let rise for about 40 minutes, or until doubled in size.
Bake for 20 to 22 minutes, or until golden. Let cool for a few minutes, then remove the buns with the aid of a spoon or a thin knife blade. Place on a wire rack.
To make the glaze: Stir the sugar, butter, milk, and vanilla in a small bowl until smooth. Add a drop or two of water if necessary. Use a pastry brush to coat each bun with glaze, or just drizzle it with a spoon (as I did).