Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Grease the mini ball baking tins. Wash, halve, stone and cut plums into small pieces.
Separate eggs. Beat the egg whites until stiff and chill. Mix 125 g softened butter and 125 g sugar with the whisk of the mixer until light creamy. Stir in the egg yolks one after the other. Briefly stir in flour with 2-3 tbsp. cream.
First fold about half of the beaten egg white into the dough, then add the plums. Fold in the rest of the beaten egg white.
Spread the dough into the moulds. Bake in a hot oven for 18-20 minutes (test with chopsticks!). Remove from the oven, allow to cool for approx. 30 minutes and turn out of the ramekins. Let them cool down.
Roast the pistachios in a pan without fat for approx. 3 minutes and remove. Caramelise 3 tablespoons of sugar in the pan, jerking the pan from time to time to distribute the sugar evenly.
Take it off the stove. Melt 1 tsp. butter in the caramel. Pour 75 g of cream. Place back on the stove and simmer until the caramel is liquid and slightly creamy, stirring frequently. Spread over the mini-spheres, sprinkle with pistachios and leave to cool.