Add the flour and icing sugar to the bowl of a food processor and process to combine. Add the butter and pulse until the mixture resembles fine breadcrumbs. Add the egg yolk and water and process until the mixture starts to come together in a ball. Remove from the food processor and form into a disc, wrap in plastic wrap and refrigerate for 30 minutes.
Meanwhile, slice the plums. You don't want them whisper thin, but you don't want them too thick and chunky either. Place the plums in a bowl along with the honey. Rub the thyme leaves between your fingers to release their flavour and add to the plums and toss well to ensure everything is coated.
Preheat the oven to 180 celsius (350 fahrenheit) and remove the pastry from the refrigerator and roll until roughly 5mm thick. Cut out 4 discs from the pastry of roughly the same size and place on a baking tray lined with baking paper. Scatter the almond meal around the centre of each disc, leaving a border. Arrange the plums on top of the almond meal. Bring up the pastry border to enclose the filling, pleating as you go. Bake for 25 minutes, or until the pastry is lightly golden. Serve with your favourite accompaniment, be that ice cream, cream or coconut cream. Personally, I just eat them hot out of the oven without any other adornments, but my husband loves them with lashings of whipped cream.