Begin the recipe by grabbing your favorite standard-size mug. Add 1 tablespoon all-purpose flour, 4 tablespoons granulated sugar, and 2 tablespoons unsweetened cocoa powder. Whisk (stir) to combine the dry ingredients together.
Add 1 large egg and 2 tablespoons of vegetable oil. Stir to combine all of the ingredients together, but try not to overmix.
Place the mug brownie into the microwave and cook for about 1 minute. Keep in mind microwaves may vary and the cooking time may need to be adjusted. After 1 minute, check the mug and microwave for an additional 10 seconds at a time, until the brownie is slightly spongy but still gooey.
Carefully remove the brownie from the microwave and allow it to sit for 1 to 2 minutes before serving. Serve warm and top with chopped walnuts and chocolate chips if you prefer. Enjoy!
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Notes
You may adjust the amount of sugar or use a sugar substitute if you prefer. Brown sugar may also be used if you prefer.
Stir in some finely chopped walnuts or pecans to the brownie mixture before placing it into the microwave.
Try not the overmix the brownie mixture or you may end up with a brownie that is dry and tough.
Lightly beat the egg in a separate small bowl for easier mixing.
Melted butter can be substituted instead of using vegetable oil.
The brownie will rise during baking, but as it cools it will settle and reduce in size, this is normal.