Place the strawberries and raspberries in one small, deep- sided bowl and the blackberries and blueberries in another.
Using a handheld blender, whizz the strawberries and raspberries, then the blackberries and blueberries until pureed. I used my Nutri Bullet to blitz the fruit, separately.
Place the oats in a microwaveable bowl with the milk and cinnamon. Heat according to pack instructions. Spoon into serving bowls.
Using a teaspoon to drizzle (see tip below) create a spiral of puree on top of the porridge, first with the strawberry puree then adding on the blackberry puree in parts. Use a skewer or the tip of a sharp knife to drag the puree out in lines all the way around the spiral. Add a few small spots of puree, scatter with pistachios and serve.
You could also use a large disposable piping bag with the end snipped to approx 1/2 cm to create the spiral.