Set the oven at 200C/gas mark 6. Wipe the plums and put them in a baking dish or roasting tin in a single layer. Sprinkle the caster sugar and ground cinnamon over the plums then tuck in the cinnamon stick and the bay leaves.
Place the baking dish in the oven and bake for 25 minutes or until the plums have started to split and a syrup has formed in the bottom of the dish. Remove the plums from the oven.
While the plums are baking, make the ricotta-maple cream. Pour the double cream into a chilled bowl and whisk until it starts to thicken. Stop when it will sit on soft folds, before it is stiff enough to stand in peaks.
Fold the ricotta into the cream with a fork carefully, making sure not to over-mix. A gentle stir with a fork is enough. Pour in the maple syrup and turn once or twice, so as to leave ribbons of syrup through the cream. Cover and chill in the fridge until the plums are ready.
Serve the baked plums while they’re warm, with a bowl of the ricotta-maple cream. Add a spoonful of the cream to the plums at the table, letting the cool cream melt into the warm, syrupy plum juices.