Place the strawberries and raspberries in a pan with the sugar, water and orange juice. Bring to the boil without stirring, then remove from the heat.
Place the gelatine in a bowl, cover with cold water and leave to soak for 5 minutes. Once softened, drain and squeeze out excess water from the gelatine. Place the gelatine back in the bowl and add a little of the warm fruit juices, stirring gently until the gelatine is completely dissolved. Pour into the fruit pan through a fine sieve (fine mesh strainer) and stir very gently.
Spoon the fruits into French bistro glasses and pour over the orange liquid from the fruit pan. Stir once more, then transfer to the refrigerator to set.
When set, decorate with halved strawberries and sprigs of mint. Serve with vanilla ice cream.