In a medium bowl, combine 1 ½ cups of all-purpose flour, ½ cup of granulated sugar, and ¼ teaspoon of fine sea salt. Pour in ½ cup of melted butter and mix until the mixture resembles coarse crumbs. Press this crust firmly into the bottom of a greased 9x13-inch baking pan. Bake at 350°F (175°C) for 12-15 minutes, until the edges are lightly golden and set.

In a medium saucepan, melt 1 cup of dark brown sugar along with ½ cup of butter over medium heat, stirring constantly until fully dissolved. Once combined, add in ½ cup of heavy cream and let it simmer gently for 4-5 minutes. Watch for the mixture to thicken slightly; it should become glossy. Remove it from the heat and mix in ½ teaspoon of flaky sea salt to enhance the flavor.

Carefully pour the luscious caramel mixture over the baked crust, spreading it evenly. In a separate bowl, mix 4 tablespoons of melted butter, 1 teaspoon of vanilla extract, and 1 cup of granulated sugar until smooth. Drizzle this butter mixture over the caramel layer, ensuring it covers as much surface area as possible for an even finish.

Allow the Salted Caramel Gooey Butter Bars to cool completely in the pan at room temperature. Once cooled, lift the bars out of the pan using parchment paper edges, and cut them into 12 squares using a sharp knife.