In the bowl of a mixer, stir together the warm water, 1 tsp sugar, and yeast. Let it sit for 5-10 minutes, until the yeast is foamy.

Stir in the milk, melted butter, salt and remaining sugar. Running your mixer on low speed with the hook attachment, gradually stir in the flour, keeping the dough smooth. Once all the flour has been incorporated, turn the mixer up to medium speed and knead the dough for 6-8 minutes.

The dough will be very sticky at first, but become more manageable as the gluten builds up. If the dough seems too moist after 3-4 minutes of kneading, you can add in more 1 tsp at a time. The end dough will pull from the sides of the bowl but stick at the bottom. It'll be tacky but not completely unmanageable.

Cover the dough and let it rise until doubled in size, about an hour.

While dough is rising, mix the brown sugar and cinnamon together in a small bowl.

Punch down the raised dough and divide it half. On a floured surface, roll out each piece of dough into a 12"x8" rectangle. Spread half (1.5 tbsp) of the softened butter over the dough and sprinkle with some of the brown sugar and cinnamon. Use your fingers to gently rub the brown sugar into the butter.

Beginning from the long end, roll the dough up tightly, jelly roll style. Cut it into six 2-inch slices and place into a greased 9x13 baking pan. Repeat with the other piece of dough.

Let the dough rise again until doubled in size and puffy, about 30-45 minutes.

Preheat the oven to 350°F and bake the cinnamon rolls for 23-25 minutes, or until they are golden brown.

Let the rolls cool on a rack while you prepare the icing. Mix the melted butter, powdered sugar, vanilla, and milk together until smooth. Add more milk if you want a thinner icing. Spread the icing over the cinnamon rolls while they are still warm. Best enjoyed immediately!