This new flavor is a sweet dream - ripe banana ice cream swirled with rich, caramel-like dulce de leche. The banana flavor is natural and creamy, not artificial, while the dulce de leche adds ribbons of deep caramel sweetness throughout every scoop.
In a medium saucepan, combine whole milk and heavy cream. Heat over medium heat until steaming and small bubbles form at the edges (do not boil), about 3-4 minutes.
In a mixing bowl, whisk together egg yolks, sugar, and salt until pale and slightly thickened. Slowly temper the hot milk mixture into the egg yolks, whisking constantly, then pour back into the saucepan.
Cook the custard base over medium-low heat, stirring constantly with a spatula, until the mixture thickens and coats the back of a spoon (170–175°F), about 5–7 minutes. Do not let it boil. Remove from heat immediately.
Blend the ripe bananas and vanilla extract with the hot custard base using a blender or immersion blender until completely smooth. Chill the mixture over an ice bath, then refrigerate until fully cold (at least 3 hours or overnight).
Churn the banana custard in an ice cream maker according to the manufacturer's instructions until softly set. For signature Baskin-Robbins texture, churn to soft-serve consistency, then fold 2/3 of the dulce de leche in by hand to create caramel ribbons. Transfer to a container, swirl in remaining dulce de leche, and gently fold to leave thick ribbons throughout.
Cover with parchment paper touching the surface and freeze until firm, at least 4–6 hours. For easy scooping, let sit at room temperature for 5 minutes before serving.