Bircher muesli with sour cherries, pistachios and buttermilk

Ollie says: 'Bircher muesli is a recipe that isn't hard to get right, but can be even easier to get wrong. It can be too thick or claggy, too sweet, or too stingy with the fruits and nuts. However, this recipe is a vibrant burst of colours, tastes and textures. Best of all, it can be made in advance and keeps well in the refrigerator. Chia seeds are not traditional in a bircher, but they do lighten the result. Soaking the dried fruits overnight along with the grains gives a much better result than adding them at the end, as they soften and plump up in the apple juice. The variations of this are endless: the recipe here is for the winter months, but you could try pear and walnut in the autumn, or apricot, flaked almonds and fragrant lemon thyme in the summer. The breezy mint lifts the dish with every mouthful. If buttermilk isn’t available, simply swap it for more yoghurt.'