Preheat the oven to 355 F.

Butter an 8x12 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 the bowl of a stand mixer, whisk together the sugars, eggs and vanilla until light and fluffy. Slowly add the melted chocolate, followed by the dry ingredients. Mix just enough to combine.

Pour into the prepared baking pan and smooth the top with an icing spatula or rubber spatula.

Bake for 20-25 minutes, until the brownies are set but with a slight wobble.

Sprinkle with a bit of flaky salt. Leave to cool completely in the pan before slicing into squares. These chocolate rye brownies keep well in an airtight container for a week or so.