Cinnamon Bubble Buns

Place water in bowl of stand mixer and sprinkle yeast over. Let stand until bubbly, 5 to 10 minutes. Stir in butter, sour cream, sugar, egg and vanilla. Beat in 2 cups of flour, the salt and baking soda until incorporated. Add remaining flour and continue to mix until a smooth, soft dough forms.
Knead dough until smooth, using the dough hook attachment, about 2-3 minutes. Cover with plastic wrap. Let rise in a warm place until doubled in size, about 1 hour.
In a small bowl, mix cinnamon and sugar for coating. In another small bowl, melt butter in microwave. Grease a 12-cup muffin pan. Roll dough into a long cylinder and then divide into 12 equal portions. Divide each of the 12 portions into 6 equal pieces and roll each piece into a ball.
For each bun, coat six balls with melted butter and then roll them in cinnamon sugar. Arrange five balls in the bottom of a prepared muffin cup. Using your fingertip, make a small well in the center and press in the sixth ball. Repeat with remaining dough and muffin cups.
Cover buns loosely with plastic wrap and let rise in a warm place until puffy and have doubled in size, about 40 minutes.
Preheat oven to 350F. Bake buns until golden, 20-22 minutes. Let cool in pan. Use a knife to help remove buns from pan.
Place buns on a wire rack. Place a piece of parchment paper underneath wire rack. In a small bowl, mix glaze ingredients and stir until smooth. Drizzle each bun with glaze.