Brush four 6 oz. ramekins with 1 Tbsp of melted butter. In small bowl, stir together the cocoa powder and 1 Tbsp flour. Sprinkle the cocoa mixture into the ramekins and rotate to evenly coat the inside. Tap out any excess. Place ramekins onto a baking sheet.
Preheat oven to 425F (not fan-assisted), if baking right away.
In medium saucepan, set over very low heat, melt the 1/4 cup butter with the chopped chocolate over very low heat, about 15 minutes, stirring often, until smooth. Remove from heat and let cool slightly. *You can also do this in the microwave, using 30 second bursts and stirring between.
Using electric hand mixer on medium-high speed or in the bowl of a stand mixer fitted with the paddle attachment, beat the white sugar with the eggs and salt, until lighter in colour and thicker, about 3 minutes. Using a rubber spatula, fold in the melted chocolate mixture until no streaks remain. Fold in the 1/4 cup flour just until no flour is visible.
Make the raspberry filling by mashing the raspberries with the raspberry jam in a small bowl. Set aside.
Spoon two-thirds of the batter batter into ramekins. Add heaping Tbsp of the raspberry mixture into the centre. Cover with remaining batter.
If making ahead, cover the ramekins with plastic wrap and refrigerate until ready to bake. Ramekins can go straight from the fridge to the oven, but do note that the cold batter may need an extra minute or so of baking.
Bake in centre of 425F oven for 12 - 16 minutes, watching closely after 10 minutes of baking and baking just until the centre is set and often a small crack will appear, but the cake should still be jiggly when moved. *Better to under-bake than over-bake, so watch closely. Cool on rack about 3 minutes.
Run sharp knife around edge of each cake to loosen. Invert dessert plate over top of ramekin; turn upside down and gently release from ramekin. Sprinkle with icing sugar to serve.
Notes
Be sure to read the notes above this Recipe Card, for substitution suggestions and tips on making this recipe.