1Preheat oven to 350° F. In a double boiler (a heatproof bowl set over a pot of simmering water) melt the butter and chocolate, stirring frequently.
2When melted, remove bowl and set aside to cool slightly. About 5-10 minutes.
3While the chocolate is cooling, grease an 8x8 baking pan with butter. Add in a strip of parchment paper cut to fit the pan with a slight overhang. And grease the parchment paper again with butter.
4To the slightly cooled chocolate, whisk in the sugar and salt.
5Once smooth, whisk in the eggs until combined.
6Using a rubber spatula, fold in the flour (do not over-mix) and then fold in the chocolate chips and nuts (if using).
7Pour batter into greased pan and spread evenly.
8Bake for 40-50 minutes. Ovens vary so start checking at 40 minutes.
9When done, the brownies will be just set if you jiggle the pan and a toothpick inserted in the middle will come out with a few moist crumbs.
10Allow to cool in the pan.
11Use the parchment overhang to lift the brownies out of the pan and use a sharp knife to cut into squares.