• For the yeast, mix warm water, yeast, and sugar together. Place in warm spot until it foams and doubles in size, about 10 minutes. For dough, warm milk and butter to 90 degrees F in saucepan over medium heat. Crack egg into small bowl, then add vanilla extract. Place all wet ingredients and yeast mixture in bowl of stand mixer, then add flour, sugar, and salt. Mix on low speed for 4 minutes. Stop and scrape down sides of bowl, if needed. Spray an 8-quart container with nonstick spray, then transfer dough to container, cover and place in warm spot to proof until dough has doubled in size, up to an hour.
• Lightly dust the work surface with flour then place proofed dough on it. Use a rolling pin to roll out dough to roughly 12x12 inches. Evenly spread butter over the surface of dough, then sprinkle with cinnamon and brown sugar. Roll dough lengthwise and gently cut dough into 1-inch pieces using a sharp knife.
• Preheat oven to 350 degrees F. Line a 15x10-inch baking pan with parchment paper, then line the tray with 12 rolls, 1 inch apart. Place in a warm spot to proof for 20 minutes. Put rolls in the oven and bake for 18 minutes. Remove rolls from oven and serve immediately or cool for 20 minutes and add icing.                                                

For Icing:

• Place all the ingredients in the bowl of a stand mixer and mix on low until incorporated, then whip on high speed until airy, about 4 minutes.