Ingredients:
- 1 cup (225g) unsalted butter
- 1 cup (200g) granulated sugar
- 1 cup (200g) brown sugar, packed
- 4 large eggs
- 1 teaspoon vanilla extract
- 1 cup (125g) all-purpose flour
- 1 cup (85g) unsweetened cocoa powder
- 1/2 teaspoon salt
- 1 cup (175g) chocolate chips or chunks (optional)

Instructions:
1. Preheat Oven:
Preheat your oven to 175°C. Grease a 9x13 inch baking pan or line it with parchment paper.

2. Melt Butter:
In a medium saucepan, melt the butter over low heat. Once melted, remove from heat and let it cool slightly.

3. Mix Sugars and Eggs:
In a large mixing bowl, combine the granulated sugar and brown sugar. Add the melted butter to the sugars and mix well. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.

4. Combine Dry Ingredients:
In a separate bowl, sift together the flour, cocoa powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

5. Add Chocolate Chips:
Fold in the chocolate chips or chunks if using.

6. Bake:
Pour the batter into the prepared baking pan and spread it evenly. Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the centre comes out with a few moist crumbs (not wet batter).

7. Cool and Serve:
Allow the brownies to cool completely in the pan before cutting into squares and serving.

Enjoy your homemade brownies!