Heat the oven to 190c (180C fan)/390F/gas 6, and line a 20cm x 22cm square tin with greaseproof paper. In a small bowl, mix the milled chia seeds with 270ml water and set aside.
Put the coconut oil and broken chocolate into a medium-sized saucepan, and set over a low heat. Stir occasionally until melted, then mix in the sugar, flour and miso, and crumble in the salt flakes.
Finally, stir in the soaked and bloomed chia seeds, then pour into the lined tin and gently shake to distribute evenly.
Bake on the middle shelf of the oven for 45 minutes, then remove. The brownies might still be a bit wobbly in the middle, but they will soon settle down as they cool and be deliciously fudgy. Leave to cool completely, then cut into 16 squares.
