If I substitute unsweetened chocolate in Nigella’s Brownie recipe how much more sugar would I need to add?
Nigella's recipe for Brownies (from HOW TO BE A DOMESTIC GODDESS) is made wiith dark/bittersweet chocolate and we suggest using, if possible, a chocolate with at least 70% cocoa solids as this gives a rich chocolate flavour.
Unsweetened chocolate, sometimes known as baking chocolate, has less sugar and is usually has 85-99% cocoa solids (depending on the brand). It is often used for baking as it will give a more pronounced chocolate flavour. The problem with substituting unsweetened chocolate into some recipes is that it has less sugar, which can affect the structure and taste, and you need to reduce slightly the amount of chocolate and increase the amount of sugar. However, as the brownie batter already contains quite a high proportion of sugar (when compared with most cake batters), we suspect you could in this specific case substitute unsweetened chocolate for the dark chocolate without changing the sugar quantity, though we have not tried the recipe with this substitution so are unable to guarantee the results.