Using a large blender, blend up the strawberries until smooth. Pour the strawberry mixture into a serving bowl and set aside. If the strawberry seeds bother you, you can pour the strawberry puree through sieve into the bowl.

Using a large blender, combine the watermelon, Greek yogurt, vanilla extract and the cinnamon. Blend until smooth. Pour into the serving bowl with the strawberry puree and stir until well blended. Cover and chill for at least 4 hours. Garnish with fresh mint leaves before serving.