Warm 250 ml whole milk and 75 g unsalted butter in a small saucepan over low heat until it reaches about 40 °C.
In a large bowl, combine 500 g strong bread flour, 75 g caster sugar, 7 g dried yeast (or 20 g fresh yeast) and a pinch of salt.
Make a well in the centre, add the warm milk mixture and 1 beaten large egg, then stir until just combined.
Turn the dough onto a lightly floured surface and knead for 8–10 minutes until smooth and elastic.
Place the dough in a greased bowl, cover and leave in a warm spot for 1–1½ hours, or until doubled in size.
Meanwhile, beat 100 g unsalted butter at room temperature with 150 g light brown sugar and 2 tbsp ground cinnamon until smooth.
Knock back the dough, then roll it out on a lightly floured surface into a rectangle about 40 × 30 cm.
Spread the cinnamon filling evenly over the dough, leaving a small border around the edges.
Starting from the long side, roll up the dough into a cylinder and cut into 12 equal pieces, each about 3–4 cm thick.
Arrange the rolls on a baking tray lined with baking parchment, cover and leave to prove for 30–45 minutes.
Preheat the oven to 180 °C (160 °C fan/Gas Mark 4) and bake the rolls for 20–25 minutes, or until golden brown.
Make the icing by mixing 150 g icing sugar with 2.5 tbsp milk (or cream cheese for a thicker glaze) and 0.5 tsp vanilla extract until smooth.
Drizzle the icing over the warm rolls and serve.