Step 1

Whisk together the flour, granulated sugar, yeast and 1 teaspoon salt in the bowl of a stand mixer fitted with the dough hook.

Step 2

Heat the milk and 4 tablespoons of the butter in a small saucepan over medium heat until the butter melts, about 1 minute. Remove from the heat and let cool until the mixture is about 120 degrees F, another minute or two. Beat in the eggs.

Step 3

Add the milk mixture to the flour mixture. Mix on medium speed until the flour is incorporated, about 3 minutes. Increase the speed to high and mix until the dough forms a ball and pulls away from the sides of the bowl, about 5 minutes.

Step 4

Divide the dough into 6 equal pieces. Tint the first piece with about 1/2 teaspoon of the red gel coloring and knead well with gloved hands until the color is vibrant, fully incorporated and no longer streaky. Continue with the remaining orange, yellow, green, blue and purple gel coloring and dough pieces, using 1/2 teaspoon of color for each piece and changing gloves between each color. Grease 6 small bowls with butter and add 1 ball of dough to each, flipping to coat. Cover the bowls with plastic wrap and put in a warm place until doubled in size, about 1 hour.

Step 5

Meanwhile, whisk the brown sugar, cinnamon and 1/2 teaspoon salt in a medium bowl. Stir in the remaining 6 tablespoons butter until well combined and spreadable; set aside. Butter a 9-by-13-inch baking dish and set aside.

Step 6

Divide each dough ball into 4 pieces and randomly drop the different color pieces onto a clean work surface, intermixing the colors. Roll out the dough to a 12-by-15-inch rectangle with one of the longer sides closest to you; the dough balls should all connect once rolled (if not, dab with a little water and pinch the edges to seal). Spread the brown sugar mixture evenly over the dough all the way to the edges. Roll up the dough tightly into a log starting with the side closest to you.

Step 7

Using a sharp knife, cut the dough into twelve 1-inch-wide rolls. Place cut-side down in the prepared baking dish. Cover tightly with plastic wrap and put in a warm place until puffy, about 45 minutes.

Step 8

Preheat the oven to 350 degrees F.

Step 9

Bake the cinnamon rolls, rotating the baking dish halfway through, until puffed and just starting to turn golden brown at the edges, about 25 minutes. Let cool in the baking dish for 10 minutes.

Step 10

Meanwhile, whisk the confectioners' sugar, cream cheese and heavy cream in a small bowl until very smooth and combined. Spread on the rolls with the back of a spoon while still warm. Sprinkle with the rainbow nonpareils.