1. Heat the oven to 350°F (175°C) with a rack in the center. Line a standard 12-cup muffin tin with 12 tulip parchment liners.

2. Melt the butter and chocolate together in a heatproof bowl, in the microwave in 30-second bursts or over a pan of barely simmering water, stirring until smooth. Let cool for 5 minutes, until warm, not hot.

3. In a large bowl, whisk the eggs, granulated sugar, brown sugar, vanilla and salt vigorously for 1 minute, until slightly thick and glossy. This helps form the crackly top.

4. Whisk in the warm chocolate mixture until smooth.

5. Sift or whisk the flour and cocoa together, then fold them in with a spatula just until no dry streaks remain.

6. Spoon about 1 heaping tablespoon of batter into each liner (about half of the batter in total). Press 3 raspberries into the batter in each liner.

7. Divide the remaining batter over the berries, covering them as much as you can.

8. Bake for 18 to 22 minutes, until the tops look set and cracked. A toothpick inserted near the center, away from a berry, should come out with moist crumbs, not wet batter.

9. Cool in the tin for 10 minutes, then lift the brownies in their liners onto a rack and cool for about 35 minutes more. They firm up as they cool.