Preheat your oven to 350°F (175°C) and prepare a 9-inch round or springform pan by greasing it lightly.

Whisk together the all-purpose flour, baking soda, and salt in a medium mixing bowl.

In a large mixing bowl, combine the melted unsalted butter, brown sugar, and granulated sugar, mixing until smooth. Add eggs and vanilla, mixing until incorporated.

Gradually add the dry mixture to the wet ingredients, folding gently. Then fold in the semi-sweet chocolate chips.

Spread the batter evenly in the prepared pan and bake for 20-25 minutes until edges are golden and center is set.

Cool the cake in the pan for about 15 minutes before turning it out onto a wire rack to cool completely.

Beat the softened unsalted butter until creamy, then add powdered sugar, heavy cream, vanilla extract, and a pinch of salt, and continue beating until light and airy.

Once the cake is cooled, frost the top generously with the buttercream and sprinkle with sea salt or chocolate chips if desired.