In a large mixing bowl using a handheld or stand mixer fitted with a paddle attachment, cream together the butter, brown sugar, salt, vanilla, and baking soda on medium-high speed. (Here’s a helpful tutorial if you need guidance on how to cream butter and sugar.) Scrape down the sides and up the bottom of the bowl and beat again as needed to combine. Add the egg and beat until light and fluffy. Add the peanut butter, beating until well blended. Scrape down the sides and up the bottom of the bowl and beat again as needed to combine. Beat in the flour and peanuts/chips on low speed until the dough is cohesive. Dough will be soft and creamy.

Cover cookie dough and chill in the refrigerator for 1 hour and up to 3 days before baking. If chilling for longer than 2 hours, allow the dough to sit at room temperature for at least 20-30 minutes before baking.

Towards the end of chill time, preheat oven to 375°F (191°C). Line large baking sheets with parchment paper or silicone baking mats. Set aside.

Drop the dough by the Tablespoonful onto the prepared baking sheets. Bake the cookies for 9-10 minutes or until very lightly browned around the edges. Cookies will appear very soft, but will become chewy and slightly crispy as they cool. Remove from the oven and allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.

In a double boiler, melt the chocolate and butter together stirring constantly over low heat. OR microwave in a medium heat-proof bowl in 20 second increments, stirring after each until completely melted. Stirring is essential as the butter/chocolate may separate otherwise. Once smooth, remove from heat and stir in the corn syrup. Dip half of each cooled cookie into the chocolate (to make a half-moon effect) and, if desired, lightly sprinkle crushed peanuts or flaky sea salt on the chocolate. Return the cookies to the cooling rack to set, about 1-2 hours. Feel free to place cookies in the refrigerator to speed up the setting time.

Dipped cookies stay fresh covered at room temperature for up to 2 days or in the refrigerator for up to 1 week.