Line a baking tray (roughly 30x20cm) with baking parchment. Make sure the paper comes up the sides — this makes pulling the bark out much easier later. The tray should feel cool to the touch.

In a large mixing bowl, combine the Greek yogurt, honey, vanilla extract, and a pinch of sea salt. Stir vigorously with a spatula until the mixture is smooth and glossy, with no streaks of honey visible. It should smell sweet and creamy, with a thick, spoonable consistency.

Pour the yogurt mixture onto the lined tray. Spread it into an even layer about 1cm thick using a spatula or the back of a spoon. The surface should look smooth and uniform, with the yogurt holding its shape without running.

Scatter the mixed berries evenly over the top. Press them gently into the yogurt so they're partially submerged — you want them to freeze into the bark, not sit on top. If using frozen berries, you'll see a slight colour bleed, which looks lovely.

Sprinkle the chopped nuts and chia seeds over the berries. Pat them down lightly so they stick. The surface should now look like a colourful mosaic, with pockets of red, blue, and green.

Place the tray flat in the freezer. Freeze for at least 4 hours, or overnight, until the bark is completely solid. When you tap the surface, it should feel rock-hard and make a dull thud sound.

Once frozen, lift the bark out using the parchment overhang. Place it on a cutting board. Let it sit at room temperature for 2-3 minutes — you'll see the edges soften slightly and the surface become a little glossy. Break or cut into 8 rough pieces. The bark should snap cleanly with a satisfying crack.

Transfer the pieces to a freezer-safe container or zip-top bag, layering with parchment to prevent sticking. Store in the freezer for up to 3 months.