Preheat the oven to 350℉. Use melted butter or non-stick cooking spray to grease an 8x8-inch pan. Set aside.
To a medium-sized bowl, add flour, cocoa powder, and salt.
In a large mixing bowl with a hand mixer, or in a stand mixer fitted with the paddle attachment, beat butter and brown sugar on medium speed until smooth. Add in egg, egg yolk, maple syrup, and vanilla and beat for another 2 minutes.
With the mixer on low speed, gradually incorporate the flour mixture. Beat just until there are no visible streaks of flour in the batter.
Pour brownie batter into the prepared pan. Use an offset spatula or back of a large spoon to spread batter to the pan’s edges. Bake in preheated oven for 35 minutes, or until a toothpick inserted into the brownies comes out dry or with a few moist crumbs.
Remove from the oven and let the brownies cool in the pan on a wire rack.
Notes
Line your baking pan with parchment to make removal easier.
Avoid overbaking. The dark color of brownies can make it tricky to know when they're finished baking. The way to know for sure is by inserting a toothpick into a brownie. Follow the chart below to create the texture you enjoy the most.
For underdone brownies, the toothpick will have a film of thick batter.
For chewy brownies, the toothpick will have a few crumbs clinging to it.
For cake-like brownies, the toothpick will come out clean.
Storage - Keep brownies in an airtight container at room temperature for up to one week. Alternatively, wrap and store in the freezer for up to 1 month.Thaw frozen brownies at room temperature, or reheat in the microwave for about a minute.