In a blender, combine ice cream, milk, chocolate syrup, and peanut butter. Blend until well-combined and pourable.
Pour into a glass, top with whipped cream if desired, and enjoy.
*Use ½ cup milk for a thicker shake, up to ¾ cup for a thinner one.*You can replace the chocolate sauce with 2 tablespoons of cocoa powder.Approximate nutritional information is for 2 servings without optional whipped cream.