Grease a 9x13 baking dish with nonstick cooking spray.
In a small saucepan, stir milk, sugar, and butter together. Heat over low heat just until butter melts and sugar dissolves. Cool to about 100-105 degrees F.
⅓ cup milk, 3 tablespoons granulated sugar, ⅓ cup unsalted butter
Pour the milk mixture into the bowl of a stand mixer.
Add the yeast and warm water.
3 ½ teaspoons instant yeast, ¾ cup warm water
Add 2 cups flour and salt. Using a dough hook, mix on low speed for about 1 minute.
½ teaspoon kosher salt
With the mixer still going, add remaining 1 cup flour. Mix about 1 ½ minutes, or until the dough starts to clean the sides of the bowl.
Knead on low speed for about 2 more minutes, or until dough is smooth and elastic. The dough will still be slightly sticky to the touch.
Place dough in a greased bowl, turning it to grease the top. Cover the dough with a clean dish towel. Let it rise in a warm place, for about 10 minutes.
While dough is rising, prepare the filling by adding sugar, cocoa powder, and cinnamon to a small bowl. Mix to combine.
½ cup granulated sugar, 2 tablespoons unsweetened cocoa powder, ½ teaspoon ground cinnamon
Once dough is done rising, roll onto a floured surface into a 12x16-inch rectangle.
Spread softened butter on top of the dough. Sprinkle top with cocoa powder mixture.
6 tablespoons unsalted butter
From the long side of the rectangle, cut dough into 12 equal strips. Roll each into a tight cinnamon roll.
Place each roll into the prepared baking dish.
Cover the dish with the towel and let rise again for about 20 minutes. Towards the end of the rise time, preheat oven to 350 degrees F.
Bake rolls for 30-35 minutes, or until golden brown.
Let rolls cool slightly while you prepare the icing.
To the bowl of a stand mixer, fitted with the paddle attachment, beat butter and cream cheese together until well combined, about 3 to 4 minutes. Scrape down the bowl.
8 ounce package cream cheese, ¼ cup unsalted butter
Add powdered sugar, cocoa powder, vanilla, and salt. Mix again until incorporated.
2 cups powdered sugar, ½ cup unsweetened cocoa powder, ½ teaspoon vanilla extract, ¼ teaspoon kosher salt
Add icing on top of chocolate rolls before serving.
Notes
Milk: I recommend whole milk for softer cinnamon rolls.
Butter: If using salted butter, decrease the salt to 1/4 teaspoon in the dough and omit in the frosting.
Yeast: Or an equal amount of active dry yeast.
Cocoa powder: Dutch-processed cocoa powder will also work.
Cream cheese: I recommend using full-fat cream cheese for the creamiest frosting.