Combine Ingredients: In a medium-sized saucepan, combine the blueberries (no need to thaw if using frozen), caster sugar, lemon juice, and water. Give it a gentle stir to mix everything together.

Heat Gently: Place the saucepan over a medium heat. Stir occasionally until the sugar has completely dissolved and the blueberries start to release their juices. This should take about 3-4 minutes.

Simmer the Compote: Bring the mixture to a gentle simmer. Reduce the heat slightly to maintain this simmer and cook for 10-12 minutes. The berries will start to burst and the mixture will begin to thicken naturally. I like to use the back of my spoon to gently crush about half of the berries against the side of the pan to create a mix of textures.

Thicken (Optional): If you prefer a much thicker, more jam-like compote, mix the cornflour with 1 tablespoon of cold water in a small bowl to create a slurry. Pour this into the simmering compote and stir continuously for another minute until it has thickened.

Remove from Heat and Add Flavour: Take the saucepan off the heat. This is the crucial moment for flavour. Stir in the vanilla extract and the fresh lemon zest. What works best for me is adding these delicate ingredients at the end, as it preserves their bright, fresh aromas.

Cool Completely: Transfer the blueberry compote to a bowl or a clean glass jar and allow it to cool to room temperature. For the best texture, I recommend chilling it in the fridge for at least an hour. It will thicken considerably as it cools.

Assemble Your Blueberry Yogurt: To serve, spoon your Greek-style yogurt into bowls. Add a generous dollop of the cooled blueberry compote on top and use a spoon to gently swirl it through the yogurt, creating beautiful purple ribbons.