Place all the filling ingredients in a pan and cook on low to medium heat for around 5 minutes until the plums are just starting to soften.
Whilst the plums are cooking, place all the crumble ingredients apart from puffed quinoa in a food processor and pulse for a few seconds to mix everything together. Add puffed quinoa and pulse 3 or 4 times just to incorporate all the quinoa. If you haven't got puffed quinoa to hand, just replace it with oats.
Transfer the cooked plums into an oven proof dish and spread evenly to cover the bottom of the dish. Top with crumble and place in the oven for 12-15 minutes until it turns golden brown. Serve whilst hot with a dollop of coconut yoghurt if you wish.