Preheat oven 180C /350F.
If your eggs aren’t at room temperature, you can add them to a bowl of warm water for a few minutes before cracking them open.
Line your baking dish with baking paper.
Add the dry ingredients to bowl, whisk together until everything is well combined.
Add eggs and oil - mix well with a large spoon until the eggs aren’t visible and there are no dry spots or lumps in the batter. Add mix-ins if using.
Pour in to the baking dish, push batter in to corners and even out the top.
Bake for 10 minutes, turn and bake for a final 10 minutes.
Remove from oven, let cool in the pan for 20 minutes, then transfer to the fridge to set for an hour or so, uncovered.
Brownies are easiest to cut when they are completely cool (trust me) and the knife is hot. Pour boiled water on to the knife, shake off excess water and push the knife down in to the brownies in one movement to cut. This minimises waste.
If you like your brownies with some extra chew, you can store the brownies uncovered in the fridge.
Brownies can be stored in the fridge for up to a week and also freeze perfectly. Defrost at room temp or heat up in the microwave.