In a jug, mix together the cream and vanilla seeds until well combined. Pour the mixture into the lolly moulds until it reaches halfway up the sides.
Finely chop three strawberries and divide them equally between the moulds. Cover the tops of the moulds with cling film, then transfer to the freezer and freeze upright for at least 1 hour, or until the cream is beginning to solidify.
Meanwhile, blend the remaining strawberries to a smooth purée in a food processor. Remove 2 tablespoons of the purée and set aside in a bowl.
Add the icing sugar and yoghurt to the remaining purée and blend until well combined.
Soak the lavender flowers in the reserved purée for at least 10 minutes, then strain and add the puree to the strawberry and yoghurt mixture.
Fill the moulds with the strawberry and yoghurt mixture and cover each one with its lid.
Freeze the lollies for at least 4 hours, or preferably overnight. To remove the lollies from the moulds, dip them in hot water for a few seconds and release them. Serve immediately.