1. Preheat the oven to 350°F (175°C). Generously grease six wells of a standard muffin tin with butter, then dust with flour or unsweetened cocoa powder, tapping out the excess. Line each well with a paper liner.

2. Set a heatproof bowl over a small saucepan of gently simmering water (make sure the bowl doesn’t touch the water). Add 8 tablespoons butter and chopped semisweet chocolate. Stir occasionally until fully melted and smooth, about 3–4 minutes. Remove from heat and let cool for 2 minutes.

3. In a large bowl, whisk together the eggs, egg yolks, granulated sugar, and salt. Beat until the mixture is pale in color and ribbons form when the whisk is lifted, about 2–3 minutes.

4. Slowly pour the slightly cooled chocolate–butter mixture into the egg mixture while continuously whisking. Continue whisking until the batter is uniform and glossy.

5. Sift the flour over the chocolate batter. Using a rubber spatula, gently fold the flour in with a cutting motion until no streaks remain. Take care not to overmix.

6. Divide 2 tablespoons of batter evenly among the six prepared wells. Place 1 teaspoon of raspberry jam in the center of each, being careful not to let it touch the sides of the tin. Top with the remaining batter so each cup is about two-thirds full.

7. Bake for 12–14 minutes, or until the edges are set but the centers still jiggle slightly when the tin is gently shaken.

8. Remove the tin from the oven and let the cupcakes rest for 5 minutes. Run a small knife around the edges of each cup to loosen, then carefully invert the cupcakes onto a wire rack. Let cool for an additional 5 minutes.

9. While the cupcakes cool, prepare the frosting. In the bowl of a stand mixer fitted with the paddle attachment (or using an electric hand mixer), beat 8 tablespoons softened butter on medium speed until creamy, about 2 minutes.

10. Reduce the mixer speed to low. Gradually add the sifted confectioners’ sugar and cocoa powder, allowing each addition to incorporate before adding more. Once combined, increase speed to medium, then pour in the raspberry puree. Beat for 2–3 minutes, until light, fluffy, and spreadable. If the frosting is too thick, add 1 teaspoon of milk; if it’s too thin, add more powdered sugar, 1 tablespoon at a time.

11. Transfer the frosting to a piping bag fitted with a large star or round tip. Pipe a generous swirl onto each cooled cupcake.

12. Top each cupcake with 2–3 fresh raspberries. Dust lightly with additional unsweetened cocoa powder just before serving.