In a small pot over medium heat, melt the butter and sugar together. Cook, stirring continuously, until the mixture reaches ‘thread stage’ (about 225 F): you’ll see little white bubbles on the sides and it will be similar in texture to molasses. Remove from heat and pour into a heatproof bowl.

Once cool, add the egg and vanilla and whisk until you have a smooth batter.

Add the flours, whisk to just combine. Fold in the chocolate.

Set dough in the fridge to rest for 24-72 hours.

An hour before you are going to bake it, remove the dough from the fridge to soften.

Preheat oven to 350 F. Line an 8” square pan or a 8” round with parchment paper.

Press the dough evenly into the pan. Add some more chocolate to the tops so some is exposed. Sprinkle on sea salt, if desired.

Bake for 25-35 minutes.

The bars will be delicate when hot, let cool then slice. Store in an airtight container.