Preheat oven to 350°F (175°C). Grease and flour two 8-inch round cake pans.

In a large bowl, cream together 1 cup unsalted butter, brown sugar, and granulated sugar until light and fluffy. Beat in eggs one at a time, then stir in 2 tsp vanilla extract.

In a separate medium bowl, whisk together all-purpose flour, baking soda, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Stir in mini chocolate chips.

Divide batter evenly between the prepared cake pans. Bake for 25-30 minutes, or until a wooden skewer inserted into the center comes out with moist crumbs.

Let cakes cool in pans for 10 minutes, then invert onto a wire rack to cool completely.

For the frosting, in a stand mixer with the paddle attachment, beat the remaining 1 cup unsalted butter (room temp) until creamy. Gradually add 3 cups powdered sugar, 1 tsp vanilla extract, and 2-3 tbsp milk, beating until smooth and fluffy. Add more powdered sugar or milk if needed to reach desired consistency.

Once cake layers are completely cool, frost between layers and all over the cake.