Make the chocolate lava filling by melting chocolate chips, heavy cream, and butter together until smooth. Cool, freeze, and shape into 6 balls.
Preheat oven to 350°F (175°C) and grease a 6-cup jumbo muffin tin.
Melt chocolate chips, butter, and unsweetened chocolate together until smooth, then let it cool slightly.
Beat eggs and sugar until thick and fluffy, then add vanilla and melted chocolate mixture.
Fold in flour and salt gently until just combined.
Divide batter into muffin cups and place one frozen lava ball in the center of each.
Cover with batter and bake for about 25 minutes until edges are set but center is soft.
Let cool for 3–5 minutes, then remove from pan carefully.
Serve warm with fresh raspberries.