Heat the oven to 170C (160C fan)/350F/gas 4. Lightly grease a 23cm x 33cm baking tin and line with a piece of greaseproof paper that overhangs the two long sides.
For the Brownies
Sift the flour, cocoa, salt and baking powder into a large bowl. Put the butter and dark chocolate in a heatproof bowl and set over a pan of simmering water (make sure the base of the bowl doesn’t touch the water), stir occasionally until fully melted, then take the bowl off the heat.
Put both sugars, the eggs and vanilla in a separate large bowl and, using an electric mixer, whisk on medium-high for four to five minutes, or until increased in volume, thick and pale. This is what will give the brownies a fudgy texture and a thin crackly crust.
Turn the mixer to low, pour in the chocolate mixture and combine. Use a spatula to fold the dry ingredients into the chocolate mixture until just the odd fleck of flour remains. Scrape into the prepared tin and spread out evenly. Sprinkle over half the pecans and half the milk chocolate pieces or chips.
Bake for 25 minutes, or until a toothpick comes out with moist crumbs attached. Leave to cool in the tin. For a fudgier brownie, once cool, chill for a couple of hours in the refrigerator.
For the Salted Caramel
Put the sugar in a small saucepan and cook over a medium heat until melted and the color of an old copper coin. Add the cream, butter and salt, and, once the bubbling has subsided, if there are any lumps, reduce the heat and stir until melted. Pour the caramel into a small, heatproof bowl and set aside for 10–15 minutes until slightly thickened.
To finish, drizzle the caramel over the brownies, sprinkle over the remaining pecans and milk chocolate, and scatter over a little extra flaked sea salt, if you’re a fan of sweet and salty. Remove from the tin and cut into squares.
Storage: Store in a sealed container for four days.Flour: You can substitute the rye for plain all purpose flour, but if you haven't tried rye, I would implore you to, it makes a very special brownie.