In a saucepan, bring the plums, sugar and lemon juice to a boil, stirring frequently. Simmer for 2 or 3 minutes. Let cool and transfer to a sealable container. Seal and refrigerate until chilled.
In a food processor, combine the flour, sugar and salt. Add the butter and pulse until the mixture resembles coarse sand. Add the egg, water and vanilla. Pulse until the dough just begins to hold together. Remove the dough from the food processor and shape into a log. Cut into 8 pieces and shape by hand into 8 discs. If the dough is too soft to work, place the discs on a plate, cover and refrigerate for about 30 minutes.
Roll out each disc to a thickness of about 3 mm (1/8 inch). Line 8 tartlet pans (about 10-cm/4-inch) with removable bottoms. Prick the dough all over with a fork. Place the tartlet shells on a baking sheet and refrigerate for 30 minutes.
With the rack in the middle position, preheat the oven to 200°C (400°F).
Bake the shells until they start to brown, about 15 minutes. Let cool completely.
White chocolate whipped cream
Melt the white chocolate in the top part of a double boiler. Remove from the heat and add 125 ml (1/2 cup) cream. Mix well. Cover and refrigerate until the mixture cools to room temperature, about 1 hour.
In a bowl, whip the remaining cream until stiff peaks form. Using a spatula, gently fold the whipped cream into the chocolate mixture. Spoon the mixture into the shortbread shells. If not serving immediately, refrigerate.
Just before serving, spoon the plum mixture over the whipped cream and drizzle with a small amount of simple syrup.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.