To make these cookies, start by preheating your oven to 350 F. Line a baking sheet with parchment paper and set it aside.
Next, prepare the brown butter. Add a small saucepan, to the stove, over medium heat, and add in the butter.
Stir the butter until it's melted - this should take approximately 2 minutes.
Watch the butter carefully as it melts and bubbles. As soon as the surface starts to turn brown and the butter smells nutty, remove it from the heat. It's important to watch it carefully, so that it doesn't burn! Set the browned butter aside to cool for 2-5 minutes.
Once the butter is cool, add it to a large mixing bowl or the bowl of a stand mixer alongside the cane sugar and brown sugar and mix to combine.
Then, add in the egg and the vanilla extract and mix again until it's smooth and glossy.
Then, fold in the gluten-free flour (or all-purpose flour, if using), and baking soda and mix again, on low (if using a stand mixer) until the flour is just incorporated and a thick dough forms. Be careful not to over-mix here, otherwise the cookies will turn out tough!
While the dough is mixing, chop the pistachios and chocolate. Then, gently fold them into the dough.
Next, grab the parchment-lined baking sheet and scoop the cookie dough into evenly-sized balls - approximately 3 tablespoons of dough each. You can do this by hand or use a cookie scoop. Add the dough balls to the parchment sheet and repeat until all the dough has been used. You should end up with 12 cookies.
Finally, transfer the tray into the oven and bake the cookies for 12-14 minutes, until the edges are browned and set.
Once they're done, remove them from the oven and allow them to cool. Garnish them with a pinch of flaky sea salt, then serve and enjoy!