Wash and halve plums, remove the stones and cut in half again.
Add to a pan with 2 tbsp of water with the cinnamon stick, gently simmer until stewed.
Add to a baking dish and level out, remove cinnamon stick.
Rub together butter, oats and ground almonds, stir in brown sugar.
Top the plum mixture with the crumble mix.
Bake at 180' until bubbling and the top is crispy and golden brown.