Preheat the oven to 350°F (177°C). Spray a 10-ounce ramekin with non-stick cooking spray and set aside.
In a small mixing bowl, whisk together the melted butter, brown sugar, and granulated sugar until well combined. Mix in the egg yolk and vanilla extract until fully combined.
Mix in the flour, baking soda, and salt until just combined, then gently stir in the chocolate chips.
Scoop the cookie dough into the prepared ramekin and press it down into one even layer. If desired, sprinkle additional chocolate chips on top and gently press them down.
Bake at 350°F for 20 to 25 minutes or until the top of the cookie is set and the edges are browned. The baking time will vary depending on the size of your ramekin. If needed, tent with foil to prevent excess browning on the top of the cookie.
Allow to cool, then serve and enjoy!
Notes
Storage Instructions: Once the cookie has cooled completely, you may cover it tightly and store it at room temperature for up to four days.To bake this recipe into 4 chocolate chip cookies:
Use softened butter instead of melted butter (you can cream the softened butter and sugars together with a mixer or fork).
Cover the cookie dough tightly and place in the freezer for 10 minutes.
Then, divide the dough into 4 equal pieces, roll into balls, and place on a baking sheet lined with parchment paper.
Bake at 350°F for 10-12 minutes or until the tops of the cookies are set and lightly browned.
Allow to cool on the baking sheet for 5-10 minutes, then transfer to a wire rack to finish cooling.