For the brownies:

1. Preheat the oven to 325ºF / 170ºC.
2. Butter or spray an 8-inch square baking pan and line it with parchment paper. I use a strip wide as the pan and line the bottom and 2 of the sides.
3. Melt butter in a large mixing bowl, preferably glass, in the microwave or over simmering water.
4. Add sugar, sifted cocoa, salt, and vanilla extract, and stir with a whisk until well mixed.
5. Add eggs, one at a time, and whisk until mixed well.
6. Add flour and whisk vigorously until the batter is shiny and smooth.
7. Bake for 20 to 25 minutes until a cake tester or toothpick comes out with moist crumbs attached, not wet. The center must jiggle. Don't overbake them. If in doubt, take them out a few minutes sooner than later. 
8. Let cool completely on a wire rack.
9. Cover with a layer of chocolate ganache. Let harden before cutting.

For the ganache:

1. Heat the cream in a small saucepan until almost starting to boil.
2. Put the chopped chocolate in a bowl and add the hot cream. Let stand for 1 minute and whisk to combine well.
3. After the chocolate has dissolved, add the milk and mix well.
4. Keep refrigerated.