Mix butter and chocolate in the bowl and you can either put it to the microwave to melt it down or in the saucepan.
Remove it from the heat and let it cool down.
Mix eggs and sugar in separate bowl and make it creamy.
Add salt to the chocolate-butter mix.
Add eggs with sugar to the rest (chocolate+butter+salt).
Add flour and walnuts (make sure you cut them into small pieces before adding).
Mix everything gently and pour it to the tray with baking paper.
Place it to the oven and set the timer for 25 min. (the time depends on how strong oven you have so I just take toothpick and check if there is still liquid when you place it in the middle of the brownie.
Notes
Let it cool down before you eat it!
I know you are impatient as you house is smelling so nice and you just want to eat this brownie, but trust me, any brownie is even better the next day after baking!