Set the Instant Pot to "saute" mode. Pour in the sweetened condensed milk, chocolate chip morsels, unsweetened cocoa powder, and the whole milk. Stir occasionally until everything has melted and smooth (about 15 minutes).
Turn off the Instant Pot and set to "keep warm" setting. Ladle hot chocolate into cups. Top with mini marshmallows and whipped cream. Enjoy.
Serving: 1c | Calories: 604kcal | Carbohydrates: 81g | Protein: 16g | Fat: 26g | Saturated Fat: 16g | Cholesterol: 51mg | Sodium: 212mg | Potassium: 608mg | Fiber: 3g | Sugar: 76g | Vitamin A: 661IU | Vitamin C: 2mg | Calcium: 500mg | Iron: 2mg