In the bowl of a stand mixer fitted with the paddle attachment, cream butter, sugar, and salt. Mix in eggs and yolk. Add in the sponge and mix until well combined.
1 cup butter, ½ cup sugar, 1 tsp salt, 2 eggs, 1 egg yolk
Switch to a hook attachment and add the remaining 2 cups of flour. Once combined, knead on medium-high speed for 3-5 minutes (the dough should not be sticking to the sides of the bowl but will still be sticking to the bottom).
2 cups all-purpose flour
Transfer the dough to a lightly greased large bowl, and cover tightly with plastic wrap. Place in the refrigerator overnight (recommended) or for about 8-12 hours. Do not go over that! If you want to enjoy cinnamon rolls the same day, cover and place the dough in a warm dark area (like inside your oven or microwave) and allow the dough to double in size for about 1-2 hours.
Line a 9x13-inch baking pan with parchment paper.
In a small bowl, mix the brown sugar and cinnamon.
¾ cup brown sugar, 2 tbsp cinnamon
On a well floured surface, roll out the dough into a 16 by 24-inch rectangle. Spread the softened butter over the dough and then sprinkle the cinnamon-sugar mixture evenly over the top, pressing it lightly into the butter so it sticks.
½ cup butter
Starting at a long end, roll the dough tightly into a log. Pinch the seam gently to seal it and position the dough seam side down. Trim off about ½-1 inch of dough from the ends as this doesn’t have any filling. Use a sharp knife to cut the dough into 12-equal pieces. To make clean cuts, I like to place the rolled dough in the fridge for a few minutes to become more firm*
Transfer the pieces to the prepared pan and place them cut side up. Cover the pan with plastic wrap and a towel and let the dough rise for 30 minutes.
Preheat the oven to 350 degrees F.
In a small saucepan over low heat or in a microwave safe bowl, heat up the cream until it is warm to the touch. Remove the plastic wrap and towel from the pan and pour the warm cream over the cinnamon rolls.
1/2 cup heavy cream
Bake in your preheated oven for 30-35 minutes or until just golden brown on the edges.