Preheat oven to 350°F. Line a 9x9” pan with foil or parchment and spray with nonstick cooking spray.
Place baking chocolates and butter in a large microwave safe bowl. Heat in 30 second increments, stirring between each, until melted and smooth (about 2 minutes depending on your microwave).
Stir sugar into chocolate mixture, then stir in eggs until well mixed. Add the vanilla, cocoa, and salt and stir until smooth, then carefully stir in the flour.
Pour batter into the prepared pan. Drop spoonfuls of the dulce de leche over the top and swirl them with a knife. Sprinkle with chocolate chips. Bake for about 28-35 minutes until a toothpick comes out with just a few crumbs an inch from the side of the pan (when dipped in the brownie, not the caramel). The center will remain jiggly on these right up until they are done baking, and even once the edges test clean, they’ll be rich and fudgy in the center.
Cool completely in the pan then cut into squares and serve. Store in an airtight container for up to 4 days or freeze for up to one month.