Heat oven to 180C/160C fan, or gas mark 4. Grease and line a 20cm square baking tin with greaseproof paper.

Melt together the chocolate and the dairy free butter. You can do this either in a microwave or Baine Marie. If using the microwave, heat it for 2 x 30 second intervals, stiring in between, following up with shorter 10 second intervals until it's all melted and evenly mixed. If using a Baine Marie, add the chocolate and butter in a bowl over a pan of simmering water, ensuring the bowl does not touch the water, and stir until evenly melted. Set aside and allow to cool slightly.

In the bowl of a standing mixer, Whisk the Aquafaba for 1-2 minutes, until it is pale, frothy, and holds soft peaks. Place in the sugar, and whisk using a medium speed for 2-3 minutes, until it is completely incorporated and leaves stiff peaks.

Pour in the melted chocolate and butter mix, and the vanilla extract and fold together until fully mixed, taking care not to beat out too much air.

Sift in the flour, cocoa powder and salt, and gently fold together until fully incorporated and lump free.

Add in the 100g of chopped chocolate or chocolate buttons, and fold in to mix evenly.

Pour into the prepared pan, and bake in the middle of the oven for 35 minutes. Gently give the tin a shake whilst it's still in the oven - if it's a bit wobbly in the middle, it's not quite done yet and needs an extra 4-5 minutes. When fully cooked, take out of the oven and allow to cool completely before removing from the pan.

Once completely cool, remove from the pan and cut into the desired portion sizes. I like to cut them into 12, but do whatever you prefer. It takes a few hours to cool completely, so do be patient - taking them out of the pan too early might ruin the end result! For even better results, place the cooled pan of brownies in the fridge for 30 - 60 mins to cool before slicing.