In a small bowl, mix the butter or dairy-free spread with the cinnamon until smooth.
Unroll the puff pastry and spread the cinnamon butter evenly over the surface, leaving a small border around the edges. Sprinkle the muscovado sugar evenly on top, then scatter the blueberries across the pastry.
Starting from one long side, gently but tightly roll the pastry into a log.
Cut the roll into 12 equal portions using a sharp knife.
Place the rolls into a lightly greased muffin tin, cut-side facing upwards, so they hold their shape while baking.
Bake for 12–15 minutes, or until puffed up and golden brown.
Allow them to cool in the tin for a few minutes before carefully transferring them to a plate using a spoon.
Dust lightly with icing sugar before serving, if desired.