Preheat your oven to 200°C (180°C fan) and grease a 20cm square baking tin. The tin should feel warm to the touch when you hold your hand a few inches above it, but not scorching. Grease the sides well — nothing sticks like a dry corner.

Mix the dry ingredients together. In a large mixing bowl, whisk the flour, caster sugar, baking powder, bicarbonate of soda, and salt. The mixture should look pale and fluffy, with no lumps of baking powder visible. You'll smell a faint, clean scent of flour.

Combine the wet ingredients. Make a well in the centre of the dry mix and pour in the room-temperature milk, melted butter, and beaten egg. Stir with a wooden spoon until a shaggy dough forms — it will look rough and slightly sticky, with a few dry patches still visible.

Knead the dough briefly. Turn the dough out onto a lightly floured surface and knead it just 8 to 10 times. The dough should feel soft and smooth, like the lobe of your ear, and bounce back slightly when you press it with a finger. Do not overwork it — we want tender rolls, not tough ones.

Roll out the dough. Using a floured rolling pin, roll the dough into a rectangle about 25cm by 30cm. The dough should be an even thickness of about 1cm across the whole surface. If it springs back, let it rest for 2 minutes, then try again.

Spread the filling. In a small bowl, mix the soft brown sugar and cinnamon until well combined. Spread the softened butter evenly over the dough rectangle, leaving a 2cm border along the top edge. Sprinkle the cinnamon-sugar mixture over the butter, pressing it gently into the butter so it sticks. You'll see a deep, rich brown layer that smells wonderfully spiced.

Roll and slice. Starting at the long edge closest to you, roll the dough tightly into a log. The seam should be pressed firmly to seal. Using a sharp serrated knife, cut the log into 9 equal slices, each about 3cm thick. The swirls should be visible and tight, with the cinnamon filling peeking out at the edges. Place the slices cut-side up in the prepared tin, spacing them evenly.

Bake the rolls. Bake for 22 to 25 minutes, until the tops are golden brown and the edges look slightly darker. The kitchen will smell like a bakery at this point — warm cinnamon and butter. When you tap a roll gently, it should feel firm but springy. Let them cool in the tin for 5 minutes before glazing.

Make the glaze and serve. In the same bowl you used for the dough (see, less washing up), whisk the icing sugar, milk, and vanilla extract until smooth and pourable. The glaze should be thick enough to coat the back of a spoon but thin enough to drizzle. Pour it over the warm rolls, letting it drip down the sides. Serve warm.