Preheat oven to 180°C (160°C fan) / 350°F
Line an 8x8 inch tin
Melt butter and dark chocolate together until smooth.
Whisk in sugar, then eggs and vanilla.
Fold in flour, cocoa powder and salt until just combined.
Pour half the batter into the tin.
Drizzle half the caramel and sprinkle half the pecans.
Add remaining batter on top.
Swirl over remaining caramel and pecans.
Lightly swirl with a knife and sprinkle flaky salt.
Bake for 30 minutes until edges are set and centre is fudgy.
Let cool completely (or slightly warm for gooey slices)
Cut into squares and enjoy!