Step 1 – Make the Dr Pepper Syrup: Pour 1 can (12 oz) of Dr Pepper into a small saucepan. Bring it to a gentle simmer over medium heat. Let it cook until reduced to about one-third of its volume (around 2 oz). This creates a thick, rich syrup. Remove from heat and let it cool completely.
Step 2 – Blend the Shake: In a blender, add 1½ cups of vanilla ice cream and the cooled Dr Pepper syrup. Blend until smooth and creamy. Taste and, if desired, add 1–2 tablespoons of cold Dr Pepper to adjust flavor or thickness, then blend again.
Step 3 – Serve and Enjoy: Pour the shake into a chilled glass. Top with whipped cream if you like, and serve immediately with a straw or long spoon. Enjoy your homemade Whataburger Dr Pepper Shake while it’s cold and creamy.