Preheat the oven to 400°F (200°C) and line a muffin tin with cupcake liners.
In a microwave-safe bowl, melt the butter and chocolate together in 30-second intervals until smooth. Let it cool slightly.
In a separate bowl, whisk together the eggs, powdered sugar, vanilla extract, and salt until well combined.
Pour the chocolate mixture into the egg mixture and stir until smooth.
Fold in the flour until just combined.
Spoon the batter into the prepared muffin tin, filling each cup halfway.
Place a small spoonful of raspberry jam in the center of each cupcake.
Cover the jam with more batter until each cupcake is 3/4 full.
Bake in the preheated oven for 12-15 minutes until the edges are set but the center is still soft.
Let the cupcakes cool for a few minutes before serving. The centers should be molten.
Serve warm and enjoy!