Lookfor sides that pull away, tap the top to feel if the brownies are firm, and look for a few cracks to tell if your brownies are done. Insert a toothpick to see if the brownies are underdone, fudgy, or overbaked based on how many crumbs cling to the tester. Stick a thermometer into the brownies to ensure that they've reached 165 °F (74 °CPutthe butter in a small microwave-safe bowl or ramekin, and microwave at 50% power (power level 5 on most microwaves) for 30 seconds. If it's not melted after that, continue to microwave in 10-seconds bursts until it is. This step is unnecessary if you're using extra virgin olive oil or a neutral oil.
Instructions Preheat the oven to 350°F (175°C) then line a 7x11 inch baking tray with parchment paper and set it aside. In a large bowl combine melted butter, oil, and both sugars. Add the eggs, vanilla and salt then whisk for about one minute until evenly combined and light in color.