Here is my classic recipe which I adopted from the Cooks Illustrated baking book. (love that book!) You could add chocolate chips to it if you wanted. The original recipe called for cake flour which I did not have any on hand. So I put 2 Tbsp of cornstarch in the bottom on the measuring cup, then fill it to the 1 cup line with all purpose flour, then just added the other 1/4 cup of flour. The top came out crisp/crumbly while the inside was moist, tender and wonderful!
Preheat the oven to 325. You can use a greased brownie pan or make an aluminum sling out of foil in a 9x13 baking pan. If so, grease the foil.
Whisk the flour, baking powder and salt in a bowl.
Melt the chopped chocolate in a microwave safe bowl at 50% for 2 minutes. Stir the chocolate and add the butter, heating at 30 second intervals until melted. Stir together. Or you could melt them on a double burner.
Once the chocolate is melted, add the sugar and whisk in well, then the eggs, one at a time. Make sure it is all thoroughly combined. Whisk in the vanilla and then mix in the flour, folding it in with a rubber spatula until smooth. Pour into the baking pan of choice. Sprinkle with nuts. In the 9x13 pan, bake from 30-35 minutes. In a brownie pan, bake about 15 minutes, then start checking. It will probably take at least 20. DO NOT OVER BAKE. Test with a toothpick and it should still have crumbs on it. Not wet batter, but not dry either. Let cool on wire rack in pan for about 2 hours. Remove foil sling from pan. Did you know it is easier to slice brownies with a plastic knife? Or so 'they' say. Mine keep breaking. Ubber strong brownies? Or weak plastic knives?