The usual procedure for brownies is, i believe, essential for the texture of denseness and chewiness.
You usually use unsweetened baking chocolate but that is pretty much not available in europe (now in italy I;ve found a special lindt "exquisite" or something like that, which is 99% chocolate, but it's marketed as some special eating chocolate for... for whom? masochists? totally unsweetened? anyway, it has a price tag equal to its classification as gourmet special food.)
I make them with cocoa.
Anyway, with chocolate, you melt it with the butter, then add the sugar (the sugar cools the butter enough so the eggs don;t cook) and then add the eggs one at a time, then the flour, salt and baking powder.
I make them with cocoa and mix the cocoa with the FLOUR not with the butter. It makes no sense to add the cocoa with the butter, because it's hard to mix in. You probably found a recipe that calls for that because someone figured that the original recipe mixes in the chocolate with the butter - but the chocolate is essentially meltable while cocoa is not. Also note that there is way more butter necessary toi compensate the lack of the cocoa butter that chocolate has.
I tried once making them with a creaming method and another time with a beating the eggs with the sugar then adding melted butter then the dry, and neither came out well - that, after all, is a cake method and these are not supposed to be cake, but fudgy.
here's my recipe
Preheat oven to 175 C or 350 F
grease a 15 inch X 10 inch low baking pan (you'll have to calculate the centimeters)
melt 250 GMS BUTTER in a large pot
ad 2 1/2 CUPS SUGAR (500 GM - yes, really that much, that's what contributes to the texture) (note a cup of sugar is 200 gms, a cup flour is `140 gms)
add 5 EGGS one at a time, mixing each in
mix together in a separate container:
1 1/4 CUP FLOUR
2/3 CUP COCOA (UNSWEETENED) (consider that a cup of flour and of cocoa is ROUGHLY 140 gms - I hate math, so you do the calculation )
1 TSP BAKING POWDER
1 TSP SALT
Add the dry ingredients all at once, mix only till combined and no flour is visible, pour into pan, cook until a toothpick inserted in the center comes out dry but with some crumbs of the brownie attached to it.
remove from oven, let cool on counter on a rack.
Cool completely before removing. no need for ice or anything, and that would probably just cause condensation and sogginess
As i said, the TRADITIONAL brownie (from when i was a kid, back in the fifties) was always with walnuts. I personally don;t like them that way, and don;t put them in, but you were asking for traditional. The commonest ones you see nowadays is without walnuts. Do them how you most enjoy them!