Firstly, brown the butter by placing the butter into a small saucepan over a medium heat. Cook, stirring every now and then, until the butter has foamed for about 5 minutes. Be careful, it will spit up quite a lot. Then pour into a large bowl - the butter should now weigh around 95g.
Add both sugars into the bowl and whisk together using an electric hand whisk until combined and with no lumps. Add the yoghurt and vanilla, then whisk for 2-3 minutes until the mixture is paler in colour. (It will look like cake mix at this point) Then add the sourdough discard and dry ingredients and mix again to combine.
Finally, chop the chocolate roughly and mix into the dough by hand. Then place a sheet of clingfilm directly onto the dough and chill in the fridge for 2 hours.
Preheat the oven to 180C/160C Fan/Gas Mark 4 and line a large baking tray with baking paper. Roll the cookie dough into balls roughly 70g in size and place 4 balls on the baking tray with space to spread. Place the remaining balls back in the fridge to chill.
Bake for 17 minutes. Then once removed, rap the baking tray down on the cooling rack to stop the cookies from puffing, and leave on the tray for 10 minutes to cool. As they're cooling, sprinkle over flaked sea salt. Then place on a cooling rack to cool completely. Repeat the process until all the balls are baked.
Cookie dough balls can be kept in the freezer for up to 1 month, and baked directly from frozen.
Keyword dark chocolate, discard, sea salt, sourdough, vegan