To make fig puree, cover about 125-150g of dried figs with boiling water (figs+water to equal 175g). Keep warm (you can microwave on low for 5 minutes or so or put in a small pan over low heat). Soak until soft (about 10 minutes) and puree in food processor or with stick blender. The puree should have a texture similar to thick batter or soft butter. If it's too thick, add a little water or if it's too thin, add more softened figs. (If you find you've made a bit more than the 175g you need for the brownies, you can use it to top toast or porridge or substitute for butter in biscuit or flapjack recipes.).
Melt butter and chocolate together in a heat-proof bowl over a pot of simmering water, or put it in the microwave on low for about two minutes (check, stir and repeat until melted).
Beat eggs, sugar and vanilla together until thick and creamy, then add 175g of the fig puree and then the chocolate/butter mixture.
Sift together flour and baking powder (add a pinch of salt if desired) into the bowl and combine.
If adding nuts, roast under grill or in a hot pan, chop and add.
Pour into baking pan or loaf tins. I use silicone, which doesn't need preparation, but a metal tin should be greased and either floured or lined with baking paper.
Bake at 180°C/350 F/gas mark 4 for about 30 minutes or until the brownie begins to crack and does not wobble when shaken. This may take slightly less or slightly more time depending on how hot your oven is and how you like your brownies (ie longer baking time makes a cakier, less fudgy brownie). Cool and cut into squares.
A note about substitutions: this recipe is amazingly robust and seems foolproof. Feel free to make prudent and appropriate substitutions as long as you keep the correct proportions of wet and dry ingredients. I often cut the sugar (by 30-50g) and just add an equal amount of flour instead. You can use prunes instead of figs, or substitute spelt flour for wheat. I once used 200g of chocolate and substituted 5 tablespoons of cocoa with an extra tablespoon of fig puree for the rest. Significant subs can be made within reason.