When buying chocolate for this recipe, splurge if you’re able as you really will taste the difference. I love Valrhona, but I used Ghiradelli 60% for these and I always find that it’s a really nice mid-range option. Claire doesn’t call for nuts in her version but I added a generous handful of walnuts so feel free to follow suit (or not). And the sprinkling of salt really does heighten all of the flavors — I wouldn’t skip this step and, in fact, I add an extra sprinkle when they come out of the oven. Claire mentions that the brownies are best eaten the day they’re baked but we had some sliced and covered on the counter for up to two days afterwards and they were just fine.
Only slightly adapted from The Violet Cookbook
Preheat the oven to 355 F. Butter an 8×12-inch baking pan and line with parchment paper.
In a heatproof bowl, melt together the butter and the chocolate over a pan of water that’s been brought to a boil and then taken off the heat. Allow the mixture to rest, stirring occasionally as it melts.
In another bowl, whisk together the cocoa, rye flour, baking powder and kosher salt.
In the bowl of a stand mixer, whisk together the sugars, eggs and vanilla until light and fluffy. Slowly add the melted chooolate, followed by the dry ingredients. Mix just enough to combine; fold in chopped walnuts. Pour into the prepared baking pan. Smooth the top with an icing spatula or rubber spatula and sprinkle with 1 teaspoon or so of big, flaky salt.
Bake for 20-25 minutes, until the brownies are set but with a slight wobble. Sprinkle with remaining bit of flaky salt. Leave to cool completely in the pan before slicing into squares.