Add the butter to a small saucepan over medium heat. Let it melt, then cook while stirring often. The butter will foam and develop golden brown bits with a nutty aroma. Remove from heat immediately and pour into a heat-safe bowl. Let it cool completely so the egg does not cook when mixed in. (Check notes for more details.)

Once the brown butter is fully cooled, add the sugar and brown sugar. Mix until smooth and well combined.

Add the room-temperature egg and vanilla extract. Mix until fully incorporated, and the mixture looks glossy.

In a separate bowl, whisk together the flour, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients. Mix just until no dry flour remains.

Fold in the chocolate chips or chopped chocolate until evenly distributed.

Cover and chill the dough for 15 minutes.

Preheat the oven to 350 degrees Fahrenheit. Use a 2-tablespoon cookie scoop to portion the dough, making about 12 cookies. Scoop onto a lined baking sheet and bake for 9 to 10 minutes.

Remove the pan from the oven and let the cookies finish cooking in the pan for 10 minutes.

Transfer the cookies to a cooling rack and let cool for about 30 minutes, or enjoy a few while they are still warm.