- With the rack in the middle position, preheat the oven to 200 °C (400 °F). Lightly butter six 125 ml (1/2 cup) ramekins and sprinkle generously with sugar.
- In a saucepan, off the heat, combine the sugar and flour. Add the milk and bring to a boil, stirring with a whisk. Simmer for about 1 minute. Remove from the heat and stir in the raspberry liqueur. Let cool.
- With a whisk, stir the egg into the cooled custard. Set aside.
- In a bowl, combine the frozen raspberries and jam. Divide among the ramekins. Set aside.
- In a bowl, beat the egg whites and cream of tartar with an electric mixer until soft peaks form. Gradually add the sugar, beating until stiff peaks form.
- With a whisk, stir about a quarter of the meringue into the pastry cream to lighten it. With a spatula, gently fold in the remaining meringue. Spoon into the ramekins (ideally up 1-cm / ½-inch to the edge) and smooth the top. Bake for 20 to 22 minutes or until the soufflés are fully risen and golden brown. Serve immediately.