Begin by creaming together 2/3 cup of unsalted butter and 2/3 cup of granulated sugar using a mixer. Beat for about 3 minutes until fluffy. Add 1 teaspoon of vanilla extract and mix until combined.

In a separate bowl, whisk together 1 and 3/4 cups of all-purpose flour and 1/4 teaspoon of salt. Gradually add this dry mixture to the creamed mixture, stirring until a soft dough forms.

Cover the cookie dough and refrigerate for about 30 minutes. Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.

Roll the chilled dough into 1-inch balls and place them on the baking sheets, ensuring 2 inches of space between each. Indent the center of each ball.

Bake for 10-12 minutes or until the edges are golden. Monitor to ensure centers remain soft.

In a medium saucepan, melt 1 cup of granulated sugar over medium heat until it turns deep amber—about 10 minutes—swirling gently. Carefully add in 6 tablespoons of unsalted butter and whisk until incorporated. Slowly whisk in 1/2 cup of heavy cream and boil for 1 minute.

Once the caramel cools, use a spoon to fill the indents of your cookies with warm caramel. Sprinkle with flaky sea salt.