Microwave butter for 45 seconds (it will be partially melted).
½ cup unsalted butter
Cream together butter and sugars on medium speed until mixture gets light and fluffy, about 2 minutes.
¼ cup brown sugar, ½ cup granulated sugar
Reduce mixer speed to low. Add egg and mix until fully incorporated, about 1 minute. (Tip: Creak egg into a glass or separate small bowl in case you get shell fragments. Much easier to get them out from there than the cookie dough!)
1 egg
Mix in vanilla.
1 tsp vanilla
Mix in baking soda.
¾ tsp baking soda
Add gradually (recommend ¼ cup at a time) and mix until all flour is incorporated.
1¼ cups all purpose flour
Mix in pistachios, then caramels.
1 cup chopped pistachios, 10 soft caramel candies
Using two spoons or a small cookie scoop, drop dough onto baking sheet (recommend lining with parchment paper) in approximately 1 tablespoon portions. Leave space between for expansion during cooking.
Bake for about 14 minutes or until cookies are golden brown. Recommend checking the cookies at the 10 minute mark, then in 2 minute increments thereafter. Various factors can cause cooking times to vary.
Remove cookies from oven. Sprinkle with fleur de sel. Transfer to a wire baking rack to cool.
Notes
Yield of 18 cookies will vary based on cookie size.