Preheat oven to 350°F and line a baking sheet with parchment paper and set aside. It is best if you use two baking sheets and rotate them for the batches. Dropping the second batch of dough on the hot cookie sheet will slightly change the structure of the cookie.
Pull the butter out of the refrigerator to sit at room temperature 15 minutes before using.
In a medium bowl, whisk together the 1¾ cup all-purpose flour, 1 (3.4oz.) box instant vanilla pudding mix, 2 tablespoons powdered milk, ½ teaspoon salt, and ½ teaspoon baking soda, and set aside.
Add 10 tablespoons of the 14 tablespoons unsalted butter to a skillet and cook over medium heat until melted. Continue cooking and stirring frequently for 2 to 3 minutes until brown bits start to form in the bottom of the pan, the top is foamy, and it has a nutty aroma. Remove from heat and stir in the remaining 4 tablespoons of butter until melted. Transfer the butter to a large heat-safe bowl or stand mixer bowl fitted with a whisk attachment.
Add ½ cup granulated sugar, ¾ cup light brown sugar, and 1 teaspoon vanilla extract to the butter and mix to combine.
Add 1 large egg and 2 large egg yolks and mix for 30 seconds. Let rest for 3 minutes, then whisk again for 30 seconds. Repeat the resting and whisking for 2 more rounds (a total of 2 minutes of whisking). The batter should be smooth, thick, and shiny when done - almost like caramel sauce.
Use a rubber spatula or paddle attachment to mix the dry ingredients into the wet ingredients for 1 minute. The dough may seem very soft, this is normal and you do not need to chill it.
Give the ½ cup roasted and salted pistachios a rough chop.
Fold in ½ cup mini semi-sweet chocolate chip, ½ cup Heath Bits 'o Brickle Toffee Bits, and ½ cup roasted and salted pistachios.
Make the topping mixture by adding ¼ cup mini semi-sweet chocolate chips, ¼ cup Heath Toffee Bits, and ¼ cup roasted and salted pistachios (chopped) to a small bowl and stir to mix.
Portion the dough with a large #16 2-ounce cookie scoop (each ball of dough will weigh about 2.9 ounces) and press the tops of each ball of dough into the topping mixture. Place dough balls 3 inches apart on the prepared baking sheet. Sprinkle with flaky sea salt if desired. Bake for 9 to 11 minutes, rotating halfway through. The cookies should look slightly cracked and only slightly brown around the edge.
Remove from the oven and allow the cookies to cool for 3 minutes on the baking sheet before transferring them to a wire rack to cool completely. Right after they come out of the oven, I like to take a large round cookie cutter and swirl it around the cookies to make them perfectly round and thicken them up a bit.