Prepare the starter: warm the milk so it’s just lukewarm, not hot. Mix with the yeast and a tablespoon of sugar, and let it sit for 10 minutes until foamy.
In a bowl, combine the flour, sugar, and salt. Add the egg and the prepared starter. Knead for 6–8 minutes using a mixer with a hook or by hand. Finally, add the soft butter and knead for another 5 minutes until the dough is smooth and elastic.
Cover the bowl and let it rest in a warm place for 1 to 1.5 hours, until the dough doubles in size.
Mix the softened butter, brown sugar, and cinnamon.
Roll out the dough into a rectangle and spread it with the prepared filling.
Using a sharp knife, cut the dough into strips and roll each one into a swirl – this is my favourite method because the rolls stay snug and retain their shape.
Place the rolls in a baking tray, leaving a little space between them. Cover and let them rise for another 30–40 minutes. Just before baking, drizzle a bit of cream over the rolls, into the gaps and on top.
Preheat the oven to 180°C.
Bake at 180°C (top and bottom heat, no fan) for 20–25 minutes, until golden brown. Finally, mix all the ingredients for the frosting and spread it over the rolls while they’re still slightly warm.