Make the yogurt the night before: heat the milk in a pot. This is my grandma's trick and it always works - stick one finger into the milk. If you're able to hold it there for 10 seconds comfortably, it's not hot enough. If you can't hold it for even a few seconds, it's too hot. The 10 second rule is key to finding the right temp.
(Too hot and it will kill the bacteria in the yogurt, and too cold and it won't activate the bacteria enough to set.)
Once the milk is at the right temperature, pour into a bowl. Add the yogurt to the milk and stir through. Cover and let sit overnight, or for at least 8-10 hours (it might need slightly longer for colder climates).
After it's set, stir through. If there's a lot of whey, hang in muslin for a few minutes before using. If not, stir and use right away.
Soak the dates in ½ cup of hot water for 15 minutes. Add dates and the water to a blender and blend to a smooth purée. Set aside.
For the compote: add frozen (no thawing necessary) or fresh berries to a saucepan over medium heat. Break them down with a spatula until just cooked, about 5-7 minutes.
Stir in the date purée, lemon juice and chia seeds if using and cook for a further 2-3 minutes. Set aside to cool slightly and use. Stays good refrigerated for about a week.
Divide the yogurt among bowls. Spoon the compote over the top and enjoy!