Preheat oven to 160°C (325°F).
In a saucepan, melt butter over low heat.
Slowly stir in sugar, making sure it is completely dissolved.
Stir in cocoa and remove from heat.
Add vanilla.
Stir in salt and mix until even.
Whisk eggs together in a separate bowl, then add to the mixture and stir well.
Add flour and stir until all of the flour is incorporated and the batter is an even colour.
Stir well for at least another 50 strokes.
Pour into a an 8"×8" pan lined with aluminum foil, leaving plenty of overhang on both sides.
Bake for about 25-30 minutes (the time varies depending on your pan type and your individual oven).
To tell when brownies are done, use a toothpick, stick it into the center, and pull it out.
The brownies need more time if there is wet batter on the toothpick.
If there are a few moist crumbs on the toothpick, the brownies are done.
Remove from the oven and let it cool down to room temperature.
Remove the brownies from the pan and let them chill in the fridge for a couple of hours.
(chilled brownies are easier to cut).See Notes.
Cut the brownies into 16 pieces.
Use a warm knife to cut, making sure to clean the blade after each cut for clean, neat edges.