Chewey Brownies

I've been experimenting brownies for about half a dozen times and I think I got the consistency I want this time. I wanted a crusty toasted topping but a soft and chewey inside with melted dark chocolates. Here is my recipe:

Ingredients:
  2-1/2 cups flour
  2 eggs beaten
  1/2 cup unsweetened cocoa
  1 stick of unsalted butter
  1 flat bar of dark chocolate
  1 cup sugar
  
Recipe:
In a bowl, add the eggs, softened butter, flour, sugar and mix thoroughly. Chop the dark chocolate bar and add to the ingredients. Brush vegetable oil on a 9 x 13 pan and pour in the mixture. Heat the oven to 350F degrees or 170C celcius and wait 5 minutes. Bake the pan for 20 to 25 minutes. Take out the pan and rest for 20 minutes then cut and serve.