Prepare the sponge by mixing granulated sugar, active dry yeast, and lukewarm water. Let it rest for about 10 minutes in a warm spot until bubbly and frothy. If no activity, wait 5 more minutes or replace the yeast if still inactive.

In a large mixing bowl, combine all-purpose flour, granulated sugar, egg, soft butter, and the yeast mixture. Mix until a rough dough forms.

Knead the dough by hand on a lightly floured surface for 10 to 15 minutes or use a stand mixer with a dough hook for the same amount of time until the dough is soft and elastic.

Cover the dough with plastic wrap and let it proof in a warm spot for 1 hour and 30 minutes or until doubled in size.

After proofing, add sprinkles and knead gently for a few seconds to incorporate.

Lightly flour a surface and roll out the dough to about half a cm (¼ inch) thick.

Spread softened butter evenly over the dough, then sprinkle brown sugar and ground cinnamon on top. Press gently with hands or a rolling pin to adhere.

Optionally, add more sprinkles on top of the filling.

Using a sharp knife, cut the dough lengthwise into strips of desired thickness and roll each strip tightly into cinnamon rolls.

Sprinkle brown sugar and cinnamon mixture on the bottom of a lined square pan.

Place the rolled cinnamon rolls in the prepared pan, leaving space between each.

Cover with plastic wrap and proof the rolls in a warm place for 30 to 45 minutes until slightly puffed.

Preheat the oven to 190°C (375°F). Before baking, splash heavy whipping cream on the rolls. Bake for 20 to 25 minutes, checking around 18 minutes for doneness.

While baking, prepare the frosting by mixing soft butter with icing sugar until smooth, then add cream cheese and mix until creamy.

Once the rolls have cooled slightly, spread the frosting evenly on top and serve.