Line a baking sheet with parchment paper.
In a medium bowl, combine the Greek yogurt, honey, and vanilla extract. Mix well until smooth.
Spread the yogurt mixture evenly onto the prepared baking sheet, creating a rectangle about 1/2 inch thick.
Scatter the mixed berries evenly over the yogurt layer. If using, sprinkle granola and chopped nuts on top.
Place the baking sheet in the freezer and freeze for at least 4 hours or until the yogurt is completely firm.
Once frozen, remove from the freezer and let sit for about 5 minutes to soften slightly.
Break the yogurt bark into pieces and serve immediately or store in an airtight container in the freezer.