Warm the cream, 70g sugar, and vanilla in a pan until the sugar dissolves and it begins to boil.
Remove from heat, stir in squeezed gelatine until dissolved, then mix in the buttermilk.
Divide 90g blueberries into five ramekins and pour the cream mixture over them.
Refrigerate for at least four hours or overnight until set.
Boil 100g sugar, 50ml water, and star anise in a pan until the syrup thickens slightly.
Remove from heat, add 100g blueberries, and leave to cool until the syrup turns red.
Loosen panna cottas with a knife, unmould onto plates, and top with blueberry sauce.