Heat the oven to 350°F and line a muffin pan with cupcake liners. The pan should be ready before the batter is mixed.
In a bowl, mix flour, cocoa powder, sugar, baking powder, and salt until the color looks even.
Add eggs, milk, and oil or melted butter. Stir just until smooth. The batter should be thick but pourable.
Spoon batter into each liner until it is about halfway full.
Add a spoonful of raspberry sauce into the center of each cup. Keep it in the middle, not touching the sides.
Cover the filling with a small amount of batter so the raspberry is hidden.
Bake until the tops look set but still soft, about 12–14 minutes. The centers should not feel firm.
Let the cupcakes cool for a few minutes. The middle will stay soft and lava-like.
Pipe or spread pink frosting on top once they are warm, not hot.
Finish with chocolate drizzle, chocolate pieces, and a fresh raspberry on each cupcake.