Heat oven to 180C/160C fan/gas 4. Halve and stone the plums, then place cut-side up in a small dish and drizzle with 1 tbsp honey and 2 tbsp water. Bake for 15 mins.
Mix the porridge oats with 1 tbsp honey, the vegetable oil, cinnamon, raisins and a pinch of salt. Squash together to make clumps (like a crumble mixture), then scatter over the plums. Return to the oven for another 15 mins.
Meanwhile, make your porridge. Top with the granola and baked plums, then drizzle over any excess juice from the dish.