Preheat the oven for the crumbles (electric oven: 200 °C/circulating air: 175 °C/gas: see manufacturer). Line a baking tray with baking paper. Roast the almonds in a pan without fat, let them cool down. Knead flour, butter, 25 g sugar, 1 pinch of salt, almonds and 20 g plum jam in a bowl with your hands to form crumbles. Spread on the baking tray. Bake in a hot oven for 10-12 minutes. Remove and let cool.
Wash, quarter, core and finely dice the apple. Chop plums finely. Whip cream until semi-solid.
Heat milk, cinnamon and 25 g sugar in a pot. Add oat flakes and let them swell at low heat for about 1 minute, stirring more often. Stir in plums and apple. Fold in 50 g plum puree and about half the cream. Fill porridge into glasses. Decorate with the rest of the cream, crumbles and candy canes as desired.