Start by browning the butter. Melt the butter in a skillet over medium heat. Stir occasionally at first. Once begins to bubble and comes to a boil, stir it constantly. It will start to foam. Continue stirring as you watch for it to turn a light, amber color and develop a nutty smell which should happen in about five minutes. Pour the brown butter into a heat safe bowl, making sure the scrape the bottom of the pan for all the bits. Pour butter into a large heat proof mixing bowl. Allow to cool before using.
Chop the chocolate and pistachios. Set aside.
In a large bowl, whisk to combine the flour, cinnamon and salt. Set aside.
Once the butter has cooled to room temperature, add the brown sugar and granulated sugar to the cooled brown butter. Stir to combine.
Stir in the vanilla extract followed by the egg and egg yolk and maple syrup.
Stir in the dry ingredients in two additions. Stir until just combined.
Stir in the chopped chocolate chips and pistachios. Do not overmix.
Cover the bowl with plastic wrap. Chill 30 minutes.
When ready to bake, preheat oven to 350 F. Line baking sheets with parchment paper. Use a 2 tablespoon cookie scoop to drop cookies on baking sheet. Place them 2 inches apart.
Bake 9-11 minutes until edges are golden and middles have puffed up. Remove from oven. Cool for 10 minutes on the baking sheet. Transfer to a cooling rack to cool completely.
Allow cookies to cool on the cookie sheet for 10 minutes before transferring them to a wire rack to cool.