In a bowl set over a double boiler, melt the chocolate and butter. Keep the heat low so that the butter doesn’t separate. Remove from the heat when the chocolate is melted. Whisk in the eggs, one at a time, combining thoroughly. Whisk in the rhubarb puree and vanilla and then give an extra whisk to bring it all together. Switch to a spatula and fold in the urfa-biber and flour. Continue to fold the ingredients together and add the Armagnac and raisins. Pour the batter into the pan and bake for 34-38 minutes. The brownies will still be a little wet in the middle but dry on the outer edges. Place on a rack to cool.