In a small saucepan over medium heat, melt the butter, stirring continuously. Let it foam until it changes from light yellow to a golden-brown hue, approximately 5 minutes. When it browns, remove it from heat and allow it to cool to room temperature.

In a mixing bowl, combine the cooled browned butter, brown sugar, and granulated sugar. Beat the mixture with an electric mixer until it achieves a smooth, well-blended consistency. Add the egg, egg yolk, and vanilla extract, mixing thoroughly.

In a separate bowl, sift together the all-purpose flour, salt, and baking soda. Gradually incorporate the flour mixture into the butter mixture, adding a spoonful at a time, until completely combined. Chill the dough for a minimum of 1 hour, or overnight for best results.

Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

Using a spoon or ice cream scoop, portion out 1-inch balls of dough. Place them on the prepared baking sheet, spacing each dough ball about 2 inches apart.

Bake in the preheated oven for 11 to 12 minutes, or until the cookie edges turn light golden brown. Remove from the oven and set aside to cool.

While the cookies cool, create the chocolate coating. In a microwave-safe bowl, heat the coconut oil for 30 seconds, then add the chocolate chips, stirring until fully melted.

Once the cookies are completely cooled, dip each one halfway into the melted chocolate, allowing the chocolate to set quickly on a clean baking sheet or wax paper. Garnish with flaky sea salt and enjoy.