Preheat oven to 350°F. Line three 8-inch cake pans with parchment paper circles and spray with baking spray.
In a large bowl, beat brown sugar, granulated sugar, oil, and butter on medium-high speed for 2-3 minutes until light. Add vanilla and eggs, one at a time, beating well after each addition. Scrape the bottom and sides of the bowl, then add the sour cream and mix well to combine.
3/4 cup (150g) granulated sugar, 3/4 cup (150g) brown sugar, 1/2 cup oil, 1/4 cup (57g) salted butter, 1 Tablespoon pure vanilla extract, 3 large eggs, 3/4 cup (184g) sour cream
Add the flour, baking powder, and salt alternately with the milk, mixing on low speed between each addition until combined.
2 1/2 cups (353g) all-purpose flour, 2 teaspoons baking powder, 1 teaspoon salt, 3/4 cup (180 mL) whole milk
Toss the mini chocolate chips with 3 teaspoons of flour, then add to the cake batter. Stir just until evenly dispersed, then divide the batter evenly between the cake pans (about 2 cups of batter per pan).
1 cup mini chocolate chips
Bake for 22 to 25 minutes until a toothpick inserted into the center of the layers comes out with just a few crumbs. Cool in the pans for 10 minutes before turning the cake layers out onto a wire cooling rack to cool completely.