Preheat oven to a moderate temprature (around 220C) Chop and set aside half a cup of both hazelnuts and cashews

Add remaining nuts to a food processor and process until a butter, if it doesn't form a butter then add a small amount of oil and process further. Continue until a butter forms.

Add chia eggs, sweetener, cocoa powder, vanilla, salt and baking powder to the processor and process until smooth, if the batter doesn't resemble a smooth cake batter then add water.

Add reserved nuts and stir into the batter

Pour batter into a suitable oven safe dish and bake until the edges are crispy but the middle is still gooey, this will take at least 30min.