Make the Butterscotch Sauce: Melt the butter in a medium saucepan over medium heat. Stir in the brown sugar and heavy cream. Then, let the mixture come to a boil and let it boil for 5 minutes. Do not stir it at all during this time. When the time is up, remove from the heat and stir in a generous pinch of flaky sea salt (to taste). Transfer to a jar or bowl to cool completely before using.

Brown the Butter: (Optional step) In a medium saucepan over medium heat, melt the butter. Turn the heat to medium-low and continue cooking the butter – stirring lazily. The butter will get foamy, then turn golden, then start to turn brown and develop a nutty/caramely sort of aroma. Once it reaches a deep golden color, pour into a heat safe container and pop into the freezer for 10-20 minutes, to cool down to room temperature.

Make the Cookie Dough: Add the room temperature melted brown butter to a mixing bowl and whisk in the melted butterscotch chips. Whisk in the sugars. Add the eggs and vanilla, and whisk until smooth and combined, about 30-45 seconds. Stir in the dry ingredients, making sure to scrape the sides and bottom of the bowl with a spatula to get any straggler bits of flour.

Rest Dough & Ball Cookies: Cover the bowl with a clean kitchen towel and let the dough rest in the fridge for 10 minutes. Preheat your oven to 365℉. Line a few cookie sheets with parchment paper. Once dough is rested, scoop into balls 60 grams in size. Roll the dough balls in granulated sugar.

Bake Cookies: Bake 5-6 cookies per cookie sheet. Bake for 10 minutes. The cookies will be slightly puffy and the edges will appear set. Gently press down on the cookies with the back of a measuring cup to make them a tad flatter, for frosting. Let the cookies cool on the baking sheet for 5-10 minutes, then transfer to a wire rack to cool completely before frosting.

Make the Frosting: In a medium bowl, beat together softened butter and cream cheese well with an electric mixer on high speed. Gradually beat in the powdered sugar, then add the butterscotch sauce, vanilla, and a pinch of salt. Mix until smooth. If your frosting becomes weepy, pop it in the fridge or freezer for 10-30 minutes to stiffen up a bit.

Assemble Cookies: Use a small cookie scoop to drop a dollop of frosting onto each cookie, then use a small offset spatula to spread it and make a swirl. Drizzle butterscotch sauce onto each cookie and add some sprinkles if desired.

Serve & Store: Enjoy once decorated! They can also be refrigerated for a day before serving once decorated if making ahead. Store leftovers in an airtight container in the fridge for 4-5 days.