Pour the wine into a plastic jug, cover with cling wrap and place in the freezer overnight.
Just before you're ready to serve the Frosé, remove wine from freezer and empty into a blender. Add the frozen strawberries and juice of half a grapefruit. Pulse until the strawberries have been liquidized.
Add the tin of grapefruit tonic and pulse for a short while to incorporate.
Add to wine or gin glass, garnish with fresh grapefruit and mint and serve immediately.
Keep the remainder of the mixture in the freezer in between servings.