In saucepan over medium heat, melt butter, stirring frequently until it turns golden brown. Remove from heat and let cool for 10–15 minutes.

In large bowl, whisk together brown butter, brown sugar and granulated sugar until smooth. Add eggs and vanilla, mixing until fully combined.

Add flour, baking soda and salt to sugar mixture and combine well.

Stir in pistachios and chocolate chips.

Form into 1-in. balls and place on baking sheet lined with parchment paper.

Bake at 350 degrees for 10 minutes.

While still warm, sprinkle with flaky sea salt and more pistachios, if desired).