Wash all the berries thoroughly under cold water. Pat them dry with a paper towel. Slice the strawberries into bite-sized pieces and set them aside with the blueberries and raspberries.
In a small mixing bowl, combine the Greek yogurt, honey (or maple syrup), and vanilla extract. Stir well until the sweetener is fully incorporated and the yogurt is smooth.
Take a clear glass or jar. Spoon about half of the sweetened Greek yogurt into the bottom of the container, smoothing it out with the back of the spoon.
Add a layer of the mixed berries over the yogurt. Sprinkle half of the granola over the berries to create a crunchy middle layer.
Repeat the process by adding the remaining yogurt, followed by the rest of the berries. Finish by topping the parfait with the remaining granola and a sprig of fresh mint if desired.