Preheat the oven to 350°F. Line two or three baking sheets with parchment paper and set aside.
Cut 1 cup unsalted butter into pieces, add it to a small saucepan, and heatover medium heat. Cook for about 8 minutes, whisking frequently as the butter browns. It will get quite foamy and bubble up a bit before it starts to smell very nutty and turn golden brown in color.. Remove from the heat and transfer to a small heat-safe dish to cool to room temperature.
Add 2 ¼ cups all-purpose flour, 1 ¼ teaspoon baking soda, and ½ teaspoon salt to a medium bowl and whisk to combine. Set aside.
Add 1 cup packed light brown sugar, ½ cup granulated sugar, and the cooled browned butter to a large bowl and beat with a hand mixer or stand mixer fitted with the paddle attachment on high speed for 1-2 minutes, until combined.
Add 1 large egg, 1 egg yolk, 2 ½ teaspoons vanilla extract, and 1 tablespoon sour cream to the sugar mixture and mix until combined, scraping down the sides and bottom of the bowl as needed.
Add the flour mixture to the sugar mixture and mix just until all the flour has been incorporated, again scraping down the sides and bottom of the bowl as needed.
Stir in the ¾ cup semi-sweet chocolate chips or chunks, ¾ cup toffee bits, and ½ cup lightly crushed saltine crackers. Cover the bowl tightly with plastic wrap and chill the dough in the refrigerator for 30 minutes.
Once chilled, use a medium cookie scoop to scoop 1 ½ tablespoon-sized balls of dough onto the baking sheets, leaving about 2 inches between them.
Bake for 10-12 minutes, until the edges are golden brown and the centers still look slightly underbaked. Immediately upon coming out of the oven, sprinkle each cookie with a pinch of flaky sea saltflaky sea salt before letting the cookies cool on the baking sheet for 2-3 minutes before transferring to a cooling rack to finish cooling.
Notes
Storage & Freezing Instructions
Storage: Store cookies in an airtight container at room temperature for up to 7 days.
Freezing Baked Cookies: Let cookies cool completely, then layer them with parchment paper in an airtight container. Freeze for up to 3 months.
Freezing Cookie Dough: Scoop dough into individual portions on a parchment-lined baking sheet and freeze until solid (about 2 hours). Transfer to a freezer-safe container and freeze for up to 3 months.
To Bake from Frozen: Bake dough straight from the freezer—just add a few extra minutes to the baking time.