1. Prepare the yogurt mixture:
In a medium bowl, combine the Greek yogurt, honey (or maple syrup), and vanilla extract. Mix well until the yogurt is smooth and well combined with the sweetener.

2. Layer the yogurt bars:
Line a baking pan or a small rectangular or square dish with parchment paper, leaving an overhang for easy removal. Pour the yogurt mixture into the pan and spread it evenly.

3. Add toppings:
Scatter the fresh mixed berries evenly over the yogurt. Gently press them into the yogurt mixture. If using, sprinkle granola and chopped nuts over the top for added texture.

4. Freeze the bars:
Place the pan in the freezer and let the yogurt bars freeze for 4–6 hours, or preferably overnight, until fully set and firm.

5. Cut into bars:
Once frozen, remove the pan from the freezer and lift the yogurt block out using the parchment paper. Place it on a cutting board and cut into bars or squares.