Marie Raynor, the chef behind The English Kitchen, adjusts all her recipes to be very small batch. Here are three brownie recipes, one of which makes 4 brownies. I have made many, many of her recipes and the only failure was Swim Bread. Fudgy Brownies will satisfy your craving without filling your cookie jar.
https://www.theenglishkitchen.co/search?q=brownie