In a large mixing bowl, combine the yogurt, agave, vanilla, lemon juice, and salt; whisk until thoroughly combined.
Transfer the yogurt mixture to the baking sheet and spread it out to an even thickness. Top with berries, and sprinkle with chopped nuts and granola, if using.
Freeze for 2 to 3 hours, or until firm.
Remove from the freezer, break it into pieces, and serve.
Nutritional info is an estimate and provided as courtesy. Values may vary according to the ingredients and tools used. Please use your preferred nutritional calculator for more detailed info.