Preheat the oven to 180 degrees Celsius.
Sift the self-raising flour (450 g) into a large bowl.
Cube the butter straight from the fridge.
Rub it into the flour until it resembles coarse breadcrumbs.
Stir in the caster sugar.
Pour in the milk and stir with a spoon until it comes together as a dough.
Transfer the dough to a floured work surface and bring it together in a ball so you can roll it out.
Roll the dough into a large rectangle using a rolling pin.
Mix the granulated sugar and cinnamon for the filling in a small bowl.
Sprinkle it all over the dough, spreading it equally around so it covers it evenly.
From the long side of the rectangle, roll up the dough carefully and tightly into a large roll, as if you are making a Swiss roll.
Cut the roll into 12 equal pieces.
Grease your baking tin with a little oil, ensuring you cover all sides and edges, to prevent sticking.
Arrange the swirls in 4 rows of 3, leaving a little room between each roll as they will rise as they bake.
Bake for 25 minutes or until light golden in colour and cooked through.
Remove the baking tin from the oven and allow to cool.
In a separate small bowl, mix the icing sugar with the 2 tablespoons of milk to make a smooth, not too runny icing.
Drizzle the icing over the cinnamon swirls and serve!